TCCM Replacement How To [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: TCCM Replacement How To


Vartz04
12-13-2008, 02:41 AM
I purchased my TCCM from GM Parts Direct. It cost about $200 Shipped.

Here is how you replace it.

First take off the panel under the steering wheel and the pannel that is below that
http://i7.photobucket.com/albums/y276/jefftheGRAFF/Trailblazer/TCCM005.jpg


This is what you will see from under neath the blue clip goes into the TCCM there are 3 different plugs that clip in there. It is right behind the metal plate that you will see when you take off the pannel, It is all the way to the drivers side.
http://i7.photobucket.com/albums/y276/jefftheGRAFF/Trailblazer/TCCM001.jpg

These are the 3 plugs after you take them out of the TCCM They unclip pretty easily but require a little contortion to get your hand up there to them. I am sure you could just take more stuff off but this wasnt too bad.

http://i7.photobucket.com/albums/y276/jefftheGRAFF/Trailblazer/TCCM002.jpg

This is how they go in the TCCM. Note, you cannot put them in before you pop the new TCCM into its bracket. This is just so you can see the order of the plugs because you won't be able to read the label on the TCCM when you put it into place.

http://i7.photobucket.com/albums/y276/jefftheGRAFF/Trailblazer/TCCM003.jpg

Clip the TCCM into its bracket, and install the plugs. The small black plug goes all the way to the passenger side, I labeled them in the drawing.

http://i7.photobucket.com/albums/y276/jefftheGRAFF/Trailblazer/TCCM004.jpg

Put the dash back together, go to the dealer and get it programed.


any questions just ask here, don't PM me

SweetD8943
12-15-2008, 12:05 PM
Great info - thank you so much for posting the process.

Any trouble driving the vehicle after swapping the TCCM out?

If you can - let us know what they get you for ($$) to do the re-programming of the TCCM at the dealership.

Thanks again - exactly what I needed to get this thing replaced on our TB.

Dave

gordinho80
12-15-2008, 12:36 PM
TCCM needs to be reprogrammed? I had an issue with mine a few months back. I was getting the Service 4WD light and the switch didnt have any indicator lights on. I swapped out the TCCM with one from ebay, No Problems since... never went to dealer...

SweetD8943
12-15-2008, 12:56 PM
Mario,

Someone, somewhere had mentioned that you do not need to get the newer, redesigned TCCM "reprogrammed" - whatever they did with the redesign eliminated the need to reprogram...not sure, but it sounds like it worked for you.

It will be interesting to see what they tell Vartz04 when he goes to the dealership...thanks for the input!

Dave

480-Pelle
12-15-2008, 03:35 PM
TCCM needs to be reprogrammed? I had an issue with mine a few months back. I was getting the Service 4WD light and the switch didnt have any indicator lights on. I swapped out the TCCM with one from ebay, No Problems since... never went to dealer...

So did I, installed a -04 TCCM on my -02 TB...no problem. :thumbsup:

//Pelle

Vartz04
12-15-2008, 11:44 PM
well I took mine to the dealer, they said they cannot communicate with the replacement. So something else is up I guess.

SweetD8943
12-16-2008, 10:00 AM
Hey Jeff -

That sucks. Question: Did you ever get a trouble code reading for the TCCM to diagnose it? My mechanic originally ran the diagnostic and came up with a trouble code - it was # CO-550, which came up as something to do with the TCCM / ECU. Sort of vague though...

Just wondering if you were going off of a specific diagnostic trouble code, or off the hunch that it was your TCCM based on your research of the problem?

Thanks -

Dave

TRAILBLAZER_GUY
01-21-2009, 01:34 PM
I know this Thread is over a month old, however i still think we need to follow up with the question asked previously, "Does another used 02 Trailblazer Module which is in current working condition a fix to install in an 02 Trailblazer with a bad TCCM?"


The Reason i ask is because i've heard that the 02 model TCCM is not Programmable... So does that mean that after the circuit is lost, it goes into sleep mode, Forever? Please share light on this since i find it difficult to understand that after a dead battery it would not work.

ToddMeister
01-23-2009, 09:33 AM
I put a working TCCM from an 03 Trailblazer EXT into our 02 Trailblazer, works just fine, we did not reprogram the 03 unit. The old one out of the 02 was dead (no lights on 4WD switch/service 4wd light, dead TCCM code) I would think another working 02 TCCM would work in TB with a bad TCCM.

I know this Thread is over a month old, however i still think we need to follow up with the question asked previously, "Does another used 02 Trailblazer Module which is in current working condition a fix to install in an 02 Trailblazer with a bad TCCM?"


The Reason i ask is because i've heard that the 02 model TCCM is not Programmable... So does that mean that after the circuit is lost, it goes into sleep mode, Forever? Please share light on this since i find it difficult to understand that after a dead battery it would not work.

booka96
01-27-2009, 05:36 PM
was wondering if the 03 and 02 tccm are interchangeable on the trailblazer. is the tccm located in the same place on the 03 as the 02. my 02 is on the drivers side and looking at another website it shows a picture of it on the passenger side http://kylestubbins.com/node/11 , they look different in the pictures. any help is appreciated

the roadie
01-27-2009, 08:08 PM
They're interchangable, and located above the closeout panel near the driver's left knee. That other site you looked at was discussing a Canadian 2003 S10 full-size Blazer. Not a GMT360 trailvoy kind of vehicle.

booka96
01-27-2009, 11:30 PM
thanks for your reply to my question, i am trying to decide which avenue to go with. i found one in a junkyard in an 03 for $75. i hear the dealer charges $275 for the part alone and that it still has to be programmed. is this true? or can i just install a new one and avoid the dealer? or can i just put in a used one and be done without having to program?
thanks for your help, i would love to avoid the stealer i mean dealer.

YukonLTZ
02-07-2009, 12:44 PM
I have a similar problem. Every now and then my 02's battery would be dead. I could not for the life of me figure out why. It would be fine for a week, a month, a day. Even fully charged it would sometimes be dead 2 hrs after the lalst time I ran it. After each dead battery the lights on the 4wd selector were out and I could not change out of 2wd. After driving for a random amount of time it would come back on and be fine til the battery died again. I broke down and took her to the dealer. They said the ignition switch was draining the battery. They changed it out..275. They checked the tccm and it is dead. The truck is going back in next week when the part gets here. GM tccm in Whitehorse Yukon?.....675$ plus labour. Guess I have to do my part to keep them out of chapter 11. After hitting this site. Im feeling a bit ill knowing I could have fixed it myself. Id tell them to go pound sand, but I already agreed to have them ship one here and have them install. Next time something is wrong Ill check TRAILVOY first. Great site people. Keep it up puleese!

the roadie
02-07-2009, 01:14 PM
...or can i just put in a used one and be done without having to program?...Sorry for the late reply. The TCCM should have the VIN programmed into it by a dealer's tech tool so it knows what gear ratio is in the vehicle. It also needs to know if it's being put into an AWD or 4WD vehicle - same TCCM is in both of them, but only the 4WD TCCM needs to control the front axle actuator. AWD vehicle's front axles are engaged all the time mechanically, and are missing the splined disconnect and actuator installed in the part-time 4WD trucks.

Many members have bought used TCCMs and plugged them in and they work fine, because statistically (I think) most of the vehicles with control problems are 4WD and even if the gear ratio is off the functional effect is minor.

... took her to the dealer. They said the ignition switch was draining the battery. They changed it out..275. Down here, you can buy a switch for US$30 and change it in a half hour. But you found that out already, I expect.They checked the tccm and it is dead. The truck is going back in next week when the part gets here. GM tccm in Whitehorse Yukon?.....675$ plus labour. $200 at parts4chevys.com. $75 on Ebay. 15 minutes to install. Then you pay the dealer 1/2-1 hour to program.Guess I have to do my part to keep them out of chapter 11. The mechanics have to eat, too. And by paying the local dealer, you keep them from begging in the streets. At least the money isn't going offshore or to Mexico. :ugh:After hitting this site. Im feeling a bit ill knowing I could have fixed it myself. Id tell them to go pound sand, but I already agreed to have them ship one here and have them install. Next time something is wrong Ill check TRAILVOY first. Great site people. Keep it up puleese!Thanks. We try. :D

YukonLTZ
02-07-2009, 03:54 PM
Hehe, true enough. Maybe I can help wake someone up who is on the "job bank" program and get them out of the lunchroom.

booka96
02-08-2009, 09:14 PM
Thank you for your replies, they are very informative and greatly appreciated. due to my frugalness, i think that i will be trying the salvage yard route and gamble with the $75 that he wants for the part. when i ever get around to it i will let you know of my outcome, since the snow has left us for the season now. i did however take the old one out to get the numbers off of it and when i reinstalled the tccm, the trailblazer did not want to start. it sounded like the timing was wayyyyy off, it finally started and worked its bugs out though, i guess some of the computer info was out of whack.

Hid-hq
03-02-2009, 07:52 PM
ok so which hARNESS ties in from the the 4wd switch to the tccm?

Working on an olds bravada 4wd swap.....I have essentially all the mechanical parts tccm 4wd switch harness etc.....

I know the tccm between the bravada and tb are the same p/n....

So thaT means that the wiring/pinout are similar if not the same,,,,,,

So can I splice into the bravada harness. and run it to the 4wd switch?

the roadie
03-02-2009, 08:08 PM
The TCCM has more features than the Bravada harness can support. Specifically, the Bravada doesn't have the front axle actuator, and its TC connector is 5-pin (no brake solenoid) versus the TB's 7-pin. But many of the connectors are the same, such as the ones on the switch and TCCM.

melonhead
06-12-2009, 07:23 PM
The directions on this post are great on how to install the TCCM. However, the photos have been removed. Is there anyway you can repost them or I can retrieve?

Thanks!

the roadie
06-12-2009, 08:04 PM
Only if he gets them rehosted. I don't trust free picture hosting, and recommend people attach pics to their threads to make sure trailvoy hosts them here for longevity.

Anyway, here's a compnine.com exploded view of the location. The TCCM is item #2. It's really quite trivial once you know about where it is on the dash panel above the driver's left knee.

http://www.compnine.com/largeimg/010302TS04-034.gif

melonhead
06-12-2009, 09:45 PM
Thank you so much! This will help immensely!

atandt3k
08-30-2009, 12:35 AM
The picture you have for the link is for a Chevy s10 Blazer, not the Trailblazer.:thumbsup:

the roadie
08-30-2009, 11:50 AM
... for a Chevy s10 Blazer,......as I pointed out in post #11. ;) Good eyes, though. There were some confusing years when they produced Trailblazer trim level Blazers (and an Envoy) on a non-GMT360 platform.

cadyshac
09-01-2009, 10:01 PM
My '02 trailblazer is experiencing this tccm problem. I did have to replace my battery and that is when the 4wd started acting up. No lights on the selector switch and no switching out of 2wd. I don't understand what the Roadie was talking about a couple of posts back about full time AWD versus 4wd vechicles. I can go from 2wd, 4hi, 4lo, and Awd and I thought all of the TB's were like this. I would like to get a junkyard tccm so if I find a vechicle with the same selector switch as mine will the tccm from it work? I have tried pulling fuse 8 but I don't know if I had it out for a full 30 seconds or not, I will try this again first.

cadyshac
09-01-2009, 10:22 PM
I may have answered my question, I am confusing A4WD (automatic) with full time all wheel drive. Basically if I get another tccm out of a junkyard will it work on my '02 TB? Does it have to be out of a TB or can it be an Envoy?

FunkZ
09-21-2009, 05:16 PM
In my 02 TB the part I pulled out of mine is 15085386 and the one I put in is the 12584313 from an Envoy.

AFAIK all of the platforms are compatible including TB, Envoy, Rainier, Bravada, Ascender. I believe that the important thing to match up when buying used is the gear ratio, which is standard 3.42 but others were optional such as 3.73 or 4.10 ratios. Or you can have it reprogrammed.

the roadie
09-21-2009, 05:39 PM
AFAIK all of the platforms are compatible including TB, Envoy, Rainier, Bravada, Ascender. Some of those models are only available in AWD. Others in true 4WD with a LO range transfer case. But you're right, they all use the same TCCM - it's programmed by the factory or the dealer as to which kind of vehicle it's controlling.I believe that the important thing to match up when buying used is the gear ratio, which is standard 3.42 but others were optional such as 3.73 or 4.10 ratios. Absolutely critical. But many junkyards have NO IDEA what gear ratio vehicle they've stripped parts off of. :thumbsup:Or you can have it reprogrammed.If you mean the TCCM, that's right. But sometimes dealers charge more for this than just buying the right one used in the first place. If you mean the differentials, regearing their ring and pinion will most likely cost more than buying the right one used in the first place.

cadyshac
09-23-2009, 01:44 PM
I found a "you pull the part" salvage yard that only wants $30 bucks for a tccm. Is there somewhere on the vechicle that I can identify what rear gear it has so I can compare it to mine? What if I get one from a vechicle with a different gear ratio? I dont use 4wd very often but do use A4wd frequently in the winter months.

the roadie
09-23-2009, 02:36 PM
Is there somewhere on the vechicle that I can identify what rear gear it has...Glove box RPO code sticker.

cadyshac
09-23-2009, 09:03 PM
Thanks for the info, I will check my code. What if I cant find a junkyard part that matches my gear ratio? What will happen if I use a tccm programed for a different ratio? My truck has 190,000 on it and I really dont want to pay the dealer to reprogram the tccm. For any of you wondering my truck looks like it has 50,000 on it the leather interior is like new and it runs like a top. I am the original owner and have taken good care of it.

the roadie
09-23-2009, 10:26 PM
I think the worst that can happen is that the algorithms are slightly off for ground speed in the A4WD mode. No sweat, because that is almost a totally worthless mode anyway. The engagement is potentially abrupt, and if you're not slipping it won't be engaged anyway. If you're on a slippery surface, you should be in 4HI. I wouldn't worry about the gear ratio. Just don't buy a flaky 2002 model.

I don't understand why so many folks see a benefit in the A4WD mode.

Vartz04
10-02-2009, 12:07 PM
http://i7.photobucket.com/albums/y276/jefftheGRAFF/2002%20Trailblazer/TCCM005.jpg

http://i7.photobucket.com/albums/y276/jefftheGRAFF/2002%20Trailblazer/TCCM004.jpg

http://i7.photobucket.com/albums/y276/jefftheGRAFF/2002%20Trailblazer/TCCM003.jpg

http://i7.photobucket.com/albums/y276/jefftheGRAFF/2002%20Trailblazer/TCCM001.jpg

http://i7.photobucket.com/albums/y276/jefftheGRAFF/2002%20Trailblazer/TCCM002.jpg

i thought I pmed these to roadie a while back, feel free to put them back in the original thread.

fredmertz
10-25-2009, 09:50 PM
First, I'd like to thank everyone in this thread for your sage advice.

Before buying a new TCCM (2002 TB LTZ with service light on and no indicator lights), I took off the panels to gauge how easy it would be to swap out the module.

I'm a bit of a newbie at doing things myself -- but I have successfully replaced the factory stereo with a bluetooth/satellite radio unit.

So here's my issue -- I had no problem getting the two panels off, but I could not figure out how to get the panel/plate underneath them off without taking off the entire dash. Is that what I need to do? I am hoping to avoid that. is the difficulty with the installation that you can't get it off?

Thanks!

cadyshac
10-26-2009, 10:45 AM
I cant see what you have removed but if you have removed two panels you should be able to access the tccm. Are you sure you need to remove something else? You definitely dont have to remove the entire dash. After locating the tccm in my vechicle it only took a couple of minutes to disassemble and remove the unit from the junk car I got mine from. Use a good light and make sure you aren't overlooking something.

fredmertz
10-26-2009, 11:45 AM
When I take off the two "external" panels there is a hard plastic panel where the driver's left knee would be. I believe I can make out the tccm behind this panel, but it seems to be very difficult to access it without taking that panel off.

Should I be able to see the tccm clearly just by removing those two panels?

Thanks

cadyshac
10-26-2009, 11:58 AM
From what I can remember I didn't take anything more than the two panels that Vartz shows in his pictures. It may be a little hard to see the tccm but look around I dont remember anything else close to it with three wire harnesses connected to it.

gregl01
10-26-2009, 12:37 PM
Yeah, I wondered the same thing. You have to reach your arm up from behind to get to the tccm. The pictures don't clearly show where its located and how to access it. Easy to fix once you get it pulled down though.

Greg

Vartz04
10-27-2009, 10:19 PM
its back up in there you have to be a kind of contorsionist to get in there and pull it out, its held on by a clip and you can unplug the harness and pop it out.

Nozzleman
11-05-2009, 12:18 PM
So I don't have any codes stored. Except for the SVC4WD light, all seems to work except it won't go into 4WDLO. Is that the typical failure mode for the TCCM or do I look for something else? On initial start up the lamp is out until I hit 15MPH. It was in 2WD when the lamp came on. The lack of a code puzzles me.

the roadie
11-05-2009, 02:12 PM
.. it won't go into 4WDLO. ...Are you in neutral and coasting less than 5 MPH when you try to go into or out of 4LO? There's an interlock.

Nozzleman
11-05-2009, 02:54 PM
Sitting still, <5MPH in neutral, doesn't make any difference. The indicator flashes an unusually long time and reverts to 4WH.
Should I get a code at the customary port or only on the TCCM?

I'll say that I have only had this vehicle for about a month, so I am still learning its habits. It has less than 60K miles. I've already gone through the gauge motor thing. Bad omens, huh?

the roadie
11-05-2009, 02:58 PM
The error code will only be on the TCCM, if you have a scan tool that can talk to it.

Did the previous owner change the transfer case fluid at 50K miles? Have you checked its level? The encoder motor is the biggest thing needed to change to 4LO, but if the transfer case hangs up mechanically, it will jam the encoder motor and explain your symptoms. Getting to a dealer or mechanic with a high end scan tool that can command the encoder motor through its entire range of motion is the thing I'd do next.

Nozzleman
11-05-2009, 03:37 PM
Bought from a GM dealer who changed the engine oil but I don't know about the TC oil.
I did the Autozone free scan but it apparently wasn't sophisticated enough to read the TCCM. I have 2 reputable shops that can read it for me but probably not for free. I'll spring for the $$.
I have to believe that it's electrical as 4WLO worked soon after I bought it for a brief test. I wasn't in 4wd mode when the service light came on. In fact, it was off the night before and came on soon after leaving my driveway in the morning. The scan will tell.
Thanks for the ideas.

Nozzleman
11-05-2009, 10:48 PM
New info. At initial turn on, the SVC4wd lamp is off. 4wdLO engages. Drive to 15-20MPH and the lamp comes on. It will not switch out of 4wdLO. Turn vehicle off then back on, the lamp is off. It now switches out of 4WDLO to what is selected. It's as if it is not receiving a speed pulse and the SVC4wd lamp locks up the selector.
Shaft speed sensor??

the roadie
11-05-2009, 10:52 PM
I think you're right. Never saw a report like that here in my time on the forum. See what the TCCM scan reveals.

Nozzleman
11-06-2009, 09:47 AM
I'll report after the scan.
Thanks for the guidance.

dbelcher
11-13-2009, 11:38 PM
I have a 2002 GMW Envoy. My 4x4 service light was on and the dash switch had no lights (other than when the vehicle first started).

I decided to pay for the dealer to troubleshoot (about $100). It was the TCCM. I had read on various posts that the 2002 model year had issues with this part. I went to the local wrecking yard today and pulled one from a 2003 Trailblazer ($50). I changed it out tonight. Mine unit was located just as others had noted...under the dash panel on the driver's side. It took me about 25 minutes to remove the panel, get my hand up to get into a position to unplug it, and reinstall the new unit and dash panel. I did not disconnect the battery. When I restarted the vehicle the service 4x4 light was off and the light 2 wheel drive light on the switch was illuminated. I did a test drive and sure enough it was switching back in and out of 4 wheel drive. Overall easy repair. I probably could have saved the $100 dealer charge for the diagnosis, but I was a bit more conservative.

the roadie
11-13-2009, 11:55 PM
Thanks for the report. 2002 TCCMs really bite. Dumb GM design team.

fredmertz
11-21-2009, 02:35 PM
So I replaced the TCCM and the service 4WD light is not off, but the 4WD indicator lights no longer turn on when the car starts and there is no indicator light. This was the original problem that led me to pulling the fuse -- it was only after I pulled the fuse that the service 4WD light turned on.

Any ideas?

the roadie
11-21-2009, 02:50 PM
Where did you obtain the TCCM you put in? Was it a known working used one? Sounds like a bad 2002 unit that won't wake up at ignition on time.

fredmertz
11-21-2009, 02:56 PM
Where did you obtain the TCCM you put in? Was it a known working used one? Sounds like a bad 2002 unit that won't wake up at ignition on time.

Bought it brand new from gmpartsdirect.com, so I assume it is new and of recent vintage.

the roadie
11-21-2009, 03:11 PM
Bought it brand new from gmpartsdirect.com, so I assume it is new and of recent vintage.Oh, sigh.......you must not have read my advicethreads like these with the proper eye for details. If you got a used one from Ebay or a recycler, it would have been programmed and ready to roll. Now you have to go to a dealer who will load the right configuration software into the module's memory to make it work. It's like buying a PC with a clean hard drive, but no Windows disk to load it up. Some dealers charge a fair price for ten minutes work - some charge a rip-off one hour minimum. Good luck.

fredmertz
11-21-2009, 03:27 PM
Oh, sigh.......you must not have read my advicethreads like these with the proper eye for details. If you got a used one from Ebay or a recycler, it would have been programmed and ready to roll. Now you have to go to a dealer who will load the right configuration software into the module's memory to make it work. It's like buying a PC with a clean hard drive, but no Windows disk to load it up. Some dealers charge a fair price for ten minutes work - some charge a rip-off one hour minimum. Good luck.

Even worse -- I read everything with a fine tooth comb -- just completely MISREAD it. I thought that 'programming" was optional, but now I see that it is "exact programming for your particular car model/trim" that is optional.

Thanks for your help -- even if I have to pay an hour worth of work for the programming, I still saved at least $300 on not paying for a diagnostic, an hour of labor (for a 5 minute job) and overpaying a dealer directly for the part.

All in, this thread has been a godsend!

Nozzleman
12-03-2009, 12:45 PM
Finally got my issue solved. C0300 and CO305.
Rodents ate the wiring of the main harness at the TC. Seven chewed on, two chewed through. Seems to be a convenient perch to sit and nibble there. Luckily none shorted. The copper was quite oxidized and appears to be from the previous owner. I can hope, anyway. Replaced all of the wires and a new connector. Rewrapped the loom and put convoluted tubing over it.

I picked up an 05 TCCM just in case. It came from a std 3.42 geared vehicle. Mine's 3.73. Does it need to be reprogrammed if I ever use it?

the roadie
12-03-2009, 01:08 PM
That's certainly a first rodent report here. Thanks for coming back and telling us what happened.

The TCCM needs to know the vehicle's gear ratio for only a couple of minor reasons. To make sure the 4LO inhibit speed it close to 5MPH ground speed, since all it knows about is driveshaft rotation speeds. This is not very important, since most folks do it while stopped anyway. The other is to optimize the algorithms used for clutch engagement under A4WD conditions. Who cares?

Personally, I advise against A4WD operation for safety's sake and the lifetime of the transfer case. The way A4WD works is to wait for front/back wheel slippage, THEN tell the encoder motor to engage the TC clutch plates to reduce the slippage. Sometimes they engage with a jolt, which can BREAK LOOSE tires that were only slipping slightly, and aggravate a skid in progress. The sudden engagement has also been linked to breaking an underdesigned clutch pressure plate bearing.

If it's slippery enough to need 4WD, then just go into 4HI. If it's not slippery enough, use 2HI and deal with the predictable and unchanging driveline performance. Offroaders with upsized tires (from 29" stock to 33-35") have effective gear ratios much lower than the one programmed into the TCCM, and AFAIK, aren't seeing any adverse effects.

Discussed in TSB #08-04-21-001B

lloydx6
12-09-2009, 11:14 AM
After reading threads about the TCCM I am still unsure if that is my problem. My selector switch does not display any lights, only drives in 2hi no matter what the switch says and does not throw any trouble codes. What is the final consensus on used and new TCCM's? Are the new ones preprogrammed, are used ones plug and play? I am going to start somewhere, I just want to make sure I am making the best choice. Thanks.

cadyshac
12-09-2009, 11:56 AM
The used ones are ready to go just plug it in. Call around and see how cheap you can get a used one for. Just don't get one out of another '02. My '02 was doing the same thing as you are describing and I put in a tccm from an '03 for $10 (bargain of the century). Works like new.

the roadie
12-09-2009, 02:24 PM
It can cost you more than $100 to have a dealer give you a FIRM diagnosis (and even then no guarantee) that it's the TCCM. And you can put in a junkyard one for less than that. Just make sure it's not a fuse (#8 under the hood) causing the lights to not come on.

If you need a free way to confirm you're making the best choice, then you have to find a local trailvoy 4WD owner to swap TCCMs with.

New ones you buy from a dealer or Internet GM parts vendors will NOT come programmed, and you have to show up at the dealer, again with +/- $100 in hand, and have them do their 10 minutes worth of magic.

For reference: GM #12590220 - $200 at parts4chevys.com, $273 list price.

Vonhendon
12-11-2009, 03:45 PM
I have an 02 Voy and sometimes mine will flash for awhile and then go to neutral,or it will be in 2hi and just not switch when I need it to. This happens mostly when it's real cold and windy. Guess i need one of them TCCM 's

the roadie
12-11-2009, 04:01 PM
Your problem could still be the switch. You could try turning it end to end 100 times or so with the power off, and see if it gets better. Or replace it first, since it's cheaper. But if you get a junkyard opportunity, pick them both up if you can, and make sure it's from 2003 or later for best reliability.

Vonhendon
12-11-2009, 04:23 PM
Thanks Roadie I was hoping to get your advice. Your knowledge on these board's is PRICELESS

eggman
12-14-2009, 08:01 PM
Thanks to your insite, I was able to read this post and fix the infamous "service 4wd" dashboard issue.

Same symptoms on an '02 trailblazer. no lights on the switch, fuse pull didn't work.

I found a used tccm mod at a junkyard for an '03 for $50 and replaced it with your pictures and instructions in less that 15 minutes!

Now to tackle the front right hub, to correct the ABS service light.

Thanks all!

NigelTufnel
12-28-2009, 05:21 PM
I'm going through a TCCM swap on my '03 Trailblazer and after several attempts to unplug the TCCM connectors from underneath the dash, I noticed an access panel on the side of the dash. Open the panel and you have direct access to the TCCM connectors. Didn't see any mention of the access panel in previous posts so I thought I'd point it out.

wholeman11
12-30-2009, 07:01 PM
hi everyone,
i'm having similar issues with my 02 trailblazer LS. Noticed that i had no indicator lights on my 4wd switch one day and after checking this site tried pulling fuse #8. after replacing, the service 4wd light came on and i now have a solid awd indicator light and a flashing 2hi indicator light. vehicle remains in 2hi no matter where there switch is. i don't hear anything when moving the switch from one position to the next and the indicator lights remain as noted. considering replacing tccm but can't find a used one and wanted to hear what others thought before buying new and having programmed. Any thoughts?

the roadie
12-30-2009, 07:16 PM
I would call junkyards, after seeing who had a trailblazer by looking on car-parts.com. Your 2002 is most likely a bad TCCM, but it would cost you more than the used one would cost to go to the dealer and have then run a communications diagnostic. You have no local buddies with a similar vehicle to trade with?

wholeman11
01-05-2010, 02:01 AM
checked that wedsite you recommended (thanks) and located a few yards in my area. Called a few of them and found a tccm from an 05 trailblazer. At first the guy i spoke to said he had a few of them in stock from 2002 - 2005 but he said i needed to check the id on the module itself to make sure one of these would match up. he proceded to give me several 4 digit numbers and told me to pull mine out and see if any of the numbers matched my current module. From what i've read, all of them are pretty much interchangable. Curious if anyone knows why he wants me to try to match the id # up.

And FYI for anyone who wants to know, $50 is what i'll be paying once i get this figured out

eggman
01-05-2010, 02:50 PM
I used this site http://www.gm-trucks.com/rpo-code-lookup/?find=gpu
I took a digital pic of the rpo sticker in the glove box and plugged in the 3 character abbreviations until I fould the one with my gearbox ratio. It started with the letter "G" I believe.

After that, I had the salvage yard confirm the rpo code on the vehicle they were taking the part out of to make sure the gear ratio was the same.

envoy02owner
01-06-2010, 11:09 PM
I have an 02 Envoy and was having the issues with the lights on the selector switch not lighting up so I replaced the TCCM with one from an 03 Envoy from a junkyard for $75. After replacing the TCCM the lights on the selector switch now light up and I can switch between all the 4 wheel modes after first starting the vehicle.

Something still seems to be acting flaky though because if I keep it in anything other then 2 wheel drive the Service 4WD light comes on after awhile and the selector switch seems to stop responding. The light of the mode that it was in at the time the Service 4WD light came on does stay illuminated. Only way to get the selector switch to respond again seems to be to turn the car off and back on again. Any ideas?

the roadie
01-06-2010, 11:46 PM
Either your front axle actuator or the encoder motor is slow to act, or dead. Search for other threads on the subject of identifying which one it is by sound.

envoy02owner
01-07-2010, 11:09 AM
Either your front axle actuator or the encoder motor is slow to act, or dead. Search for other threads on the subject of identifying which one it is by sound.

So I've been reading about listening to the noises made when switching the 4WD selector switch. The comments seem to say to do this with the engine off and the ignition in the on position. The only time the lights on my selector switch light up and the only time noises are made when moving the selector switch is when the engine is running. From what I have been reading this does not seem to be normal behavior, is it?

Also, did a little more testing and it seems that the only time the Service 4WD light comes on and the switch stops responding is when I am in the A4WD mode. 2WD, 4HI, and 4LO seem to work fine. In the past I have noticed when in A4WD that the wheels bite when turning so it acts like it is not disengaging when it should. Maybe that is why it is throwing the Service 4WD light on and making the switch stop responding?

Guess the cheapest solution is to not use A4WD which I have read is recommended anyway.

the roadie
01-07-2010, 02:57 PM
Your behavior is not normal.

Did you change transfer case fluid at 50K as required? How is the level now? You might have encoder motor problems or grabby TC clutches to get full engagement in A4WD mode. Hard to tell without having the dealer command the encoder motor through its paces with a tech tool and see what's up.

envoy02owner
01-07-2010, 03:06 PM
Your behavior is not normal.

Did you change transfer case fluid at 50K as required? How is the level now? You might have encoder motor problems or grabby TC clutches to get full engagement in A4WD mode. Hard to tell without having the dealer command the encoder motor through its paces with a tech tool and see what's up.


I have not had the transfer case fluid changed so I will get that done and see what happens after that. Thanks for the information.

envoy02owner
01-07-2010, 06:52 PM
Your behavior is not normal.

Did you change transfer case fluid at 50K as required? How is the level now? You might have encoder motor problems or grabby TC clutches to get full engagement in A4WD mode. Hard to tell without having the dealer command the encoder motor through its paces with a tech tool and see what's up.

Hey Roadie a little more information for my selector switch lights not coming on with the ignition in the Run position. It appears there are other electric components that are not coming on as well. I noticed the Radio, odometer display, 4WD selector lights, and all of the gauges (they don't move at all) remain off with the ignition in the Run position. If you start the vehicle all of these components come to life and work fine. With the ignition in the run position I do get the Service vehicle Soon light and the parking break light on the dash to come on and all interior and exterior lights come on. Any idea on what is going on there?

the roadie
01-07-2010, 07:39 PM
Start with the ignition switch, then. Usually $28 at any aftermarket store. High failure rate item blamed on all sorts of flaky electrical issues.

http://forums.trailvoy.com/showthread.php?t=61278

cntinuum
01-17-2010, 08:36 PM
Greetings, read through this entire thread. Is the tccm behind this panel in the picture? I couldn't see of feel it or see the loom of cables to it. In one post, they talk about an access panel on the side of the lower dash extension. I can see that this corner piece is a separate piece from the top of the dash assembly. Wasn't clear to me how to remove it. Wife wanted the car so I put the dash pieces back and will wait for another chance to find the tccm.
"The only that happens fast, is damage."
-Dave

fredmertz
01-17-2010, 09:05 PM
You need to reach up and around the bottom of that big panel. You won't see it, but you can pull out the unit and it will hang down on its cables.

cntinuum
01-17-2010, 09:16 PM
Thanks, will give it a go

envoy02owner
01-18-2010, 08:16 PM
Greetings, read through this entire thread. Is the tccm behind this panel in the picture? I couldn't see of feel it or see the loom of cables to it. In one post, they talk about an access panel on the side of the lower dash extension. I can see that this corner piece is a separate piece from the top of the dash assembly. Wasn't clear to me how to remove it. Wife wanted the car so I put the dash pieces back and will wait for another chance to find the tccm.
"The only that happens fast, is damage."
-Dave


On the side of the dash you can see where a panel is cut out, just use a flat head screwdriver and you can pry it out. It makes it a lot easier to see the TCM and to know where your hand is at under the dash.

FunkZ
01-18-2010, 08:59 PM
It looks like the original pictures were moved or a folder renamed:

http://media.photobucket.com/image/tccm%20trailblazer/jefftheGRAFF/2002%20Trailblazer/TCCM001.jpg
http://media.photobucket.com/image/tccm%20trailblazer/jefftheGRAFF/2002%20Trailblazer/TCCM002.jpg
http://media.photobucket.com/image/tccm%20trailblazer/jefftheGRAFF/2002%20Trailblazer/TCCM003.jpg
http://media.photobucket.com/image/tccm%20trailblazer/jefftheGRAFF/2002%20Trailblazer/TCCM004.jpg
http://media.photobucket.com/image/tccm%20trailblazer/jefftheGRAFF/2002%20Trailblazer/TCCM005.jpg

cntinuum
01-21-2010, 01:00 AM
On the side of the dash you can see where a panel is cut out, just use a flat head screwdriver and you can pry it out. It makes it a lot easier to see the TCM and to know where your hand is at under the dash. I don't think I could have got the tccm back into place w/o the access panel being open. It was a pita to get the holder to snap back in the slots. The visibility through the access panel was very helpful. In the picture, you can see the tccm plugs, barely and the black clips on the bracket coming thru the aluminum mount.

FplcMan
01-27-2010, 10:49 PM
I had the same problem. My service 4wd light would come on. Took it to the dealer and they replaced the TCCM. Worked for about a month and now it is back on... The service 4wd light is on and no lights on the control. I have a 2004 XUV... It cost me $300 to get it replaced and now this. I have 200K on the truck. Just had the trans and engine replaced. It was cheaper to replace then fix. Dealership did it on the side for me. Any ideas why it would happen again?
Thanks

cntinuum
01-28-2010, 12:32 AM
I had the same problem. My service 4wd light would come on. Took it to the dealer and they replaced the TCCM. Worked for about a month and now it is back on... The service 4wd light is on and no lights on the control. I have a 2004 XUV... It cost me $300 to get it replaced and now this. I have 200K on the truck. Just had the trans and engine replaced. It was cheaper to replace then fix. Dealership did it on the side for me. Any ideas why it would happen again?
ThanksIn short, no. Given my experience, I have bought a scanner and it is on its way so I can debug this rig without a trip to the shop. I would start by scanning to see what codes are set and go from there. Did you get a warrantee on the TCCM? If it failed, they should replace and reprogram the unit. http://forums.trailvoy.com/showthread.php?t=64219&page=4 post #31 from "the roadie" 'I still think it's the TCCM because a dead one won't light up any of the mode lamps. '
Do you hear anything when you move the switch to different positions? Some suggest 'exercising' the switch by rotating it all the way left and all the way right up to 100 times and see if that makes a difference. http://forums.trailvoy.com/showthread.php?t=68359 is a thread where you can see the insides of the switch.
Got a friend with a trailblazer/envoy that you can swap tccm's with? Easy to change and takes about 10 minutes after you do it once.
good luck!
-Dave

FplcMan
01-28-2010, 09:25 AM
In short, no. Given my experience, I have bought a scanner and it is on its way so I can debug this rig without a trip to the shop. I would start by scanning to see what codes are set and go from there. Did you get a warrantee on the TCCM? If it failed, they should replace and reprogram the unit. http://forums.trailvoy.com/showthread.php?t=64219&page=4 post #31 from "the roadie" 'I still think it's the TCCM because a dead one won't light up any of the mode lamps. '
Do you hear anything when you move the switch to different positions? Some suggest 'exercising' the switch by rotating it all the way left and all the way right up to 100 times and see if that makes a difference. http://forums.trailvoy.com/showthread.php?t=68359 is a thread where you can see the insides of the switch.
Got a friend with a trailblazer/envoy that you can swap tccm's with? Easy to change and takes about 10 minutes after you do it once.
good luck!
-Dave


Going to the Dealership on Friday. I was not using it. It just comes on when it wants to. When the light is off I did change the positions and it made the correct sounds. I will post back what the dealership says. They better not charge me that $100 fee to test it.

Confusedgarage
12-08-2010, 10:05 AM
Huge thanks to Rhoadie and all those for the info. I just fixed this last night.

I had the Serv. 4wd light on for weeks. From the info on here with the newer part # I called my junkyard and had a newer 04 Envoy tccm mailed over for $75. Just popped off the knee panel, put my head on the floor looking up with a light from where the pedals are. You can see you simply squeeze the tabs on either end of the box, and it will pull out. Then you swap the clips over to the new one and pop it back in. It really takes all of 10-15 minutes, and I was in the cold at night. No more light, it all works awesome. Thanks fellas, hope others do this on their own and save money too. It is super easy.:thumbsup:

r-charger
02-11-2011, 07:02 AM
I too have fixed my tccm problem and O2 error codes (bought aftermarket.....first, ........acdelco to fix) thanks to everyones help (first post). Curious though, my tccm went shortly after I replaced my battery as well. coincidence? Someone else posted the same experience.:bonk:

Confusedgarage
02-11-2011, 09:31 AM
Yep, mine started acting up right after I changed the battery. It was also approaching winter and I noticed the colder the morning the more likely the light was on. Who knows, for $70 and 10 minutes Im ok with that type of issue.

george_
02-12-2011, 09:01 PM
i just changed out my old tccm with a new one. it was a little tricky but can be done by most people. i have a 2002 chev trail blazer ltz. my problem was that i could not engage my 4x4. the yellow light was not on for any of the four settings. eg. 4 hi 4 low ect. my tuck was a two wheel drive while the light was out and could not be changed. i took out the bottom pannel by the gas pettal and breaks. there was three bolts and some wires that needed to be taken off. than i removed the plastic pannel below the steering wheel. there where four bolts there. than i took a screw driver and removed the little pannel on the side of the dash that can only be seen with the driver door open. you must pry open the side closer to the driver top and bottom. once open you will be able to see the bottom of the tccm. there will be three wires going into it. i recommed to labble the two blue connectors for when the new tccm is installed. to remove the old you must lift up the tccm. there are two plastic clips that hold it on to the inside of the dash. the tccm is held there by a clamp. it may be a little tricky getting it out but harder to put back in. once you remove the old take the clamp off of it. attach that clamp to the new tccm. plug in the wires to the new tccm. now the trick part begins, you with have to play with it for a while to get it back to its original position. this took the longest of all the steps. once back in re atach all the pannels.

QUESTION - once the new tccm was installed there was still no light on the 4x4 switch. do i need to pull the fueses to get it out of sleeper mode? or is it when i get my TCCM programed by GM will the light reapear? thanks for the help

RECOMENDATION- i bought my tccm from shopgmparts.com i found there where the cheapest. i paid $ 180 US dollar for it. i also noticed alot of there other parts where cheaper than most sites and the ship internationally:woot:

the roadie
02-12-2011, 09:07 PM
QUESTION - once the new tccm was installed there was still no light on the 4x4 switch. do i need to pull the fueses to get it out of sleeper mode? or is it when i get my TCCM programed by GM will the light reapear? thanks for the help If you got a virgin one from a GM supplier, you need to spend more money at a dealer to get it programmed. Sorry. They could have made them more plug and play, but no. Almost every other piece of consumer gear out here can be reflashed by plugging in a USB cable, but cars have to be made "special" because a mess-up (like the transfer case going into 4LO while on a freeway at 80 MPH) could kill people.

shaun4282
06-14-2011, 02:17 AM
Hey all,
Read this entire thread and I think that my S4WD light and no lights on in the switch might be the problem, but will check the fuze first! :duh: Again, a big thank you to all who input on this, this site has saved me a TON!!!!!
:woot: :grouphug:

rayboy55
07-22-2011, 09:58 AM
Just changed out my TCCM. I picked one from up a local salvage yard for $60. It came from an 04 Envoy. Plugged it in and I am back in business. Service 4WD went off and my indicator lights came back on. Shifts into 4 WD perfect now. Thanks Trailvoy!:woohoo:

NYDeer
09-02-2011, 10:57 PM
Great site, shopping TCCMs now. During Hurricane Irene, while contemplating running a 10-12" puddle, looked to the 4wd switch, noticed 'No Light' on the4WD selector switch, & backed out with a u turn.. Popped on here today finally, pulled Fuse 8, now switch illuminates during bulb check, then goes dark. 'Service 4WD' on dash now illuminated, it wasn't before.. Going to swap TCCM & report back.

airboss
09-09-2011, 11:40 PM
Good luck! My problem is I have a S4WD dash light, All the selector switch lights WORK JUST FINE but it won't shift. 2HI light id on solid, and when attempting to select any other mode, the 2HI light stays on, the new selected mode just blinks forever until I return it to 2HI, which stays on solid..WTF???? I hear the correct noises....

the roadie
09-10-2011, 01:55 AM
The noises might be there, but either the front axle actuator or the transfer case encoder motor isn't moving to the position the TCCM is commanding them to. A dealer or advanced independent mechanic with a suitable scan tool can talk to the TCCM and troubleshoot it precisely. Or you can take stuff off and shotgun it.

Dave_Stumph
09-10-2011, 11:10 AM
I just bought my used 2002 envoy at 270000km and it runs great except for 2 things. Bought as a second vehicle to tow :)
I noticed like many others that I do not have a light on my switch to indicate my drive mode. So reading up on the issue here and found a couple things. I first disconnected the battery for a while (40 min) Then pulled fuse 8 and 48 to try and get the TCCM out of "sleep mode" no luck. I then went to the junk yard and found a few of them to try before I purchased :) 1 was out of a TB 03 and the other a Enovy 04. Plugged em both in and still no lights on the switch when I turned the ignition on. At this point I was hoping for a SEL light to come on........but nothing. I'm out of cheep options to check.
Oh ya, prior to all of this I had gotten a saftey done and my mechanic did tell me that he did a diagnostic on the 4x4 and said the the switch was communicating to the tccm but the tccm wasn't communicating, hence the swap at the junk yard. He did pull some codes.....I'll see if i still have the paper and post.
If anyone has any ideas of what to check next please feel free :crazy:

The second issuse is the stalling at low idle.....i'll chime in the correct thread for that latter today once I clean out the tb (witch is new by previous owner) and look at the cpas?

EDIT: Any one know how much voltage is going though the number 8 fuse? I tested with the mult-meter and i read 0vdc. I also checked the voltage going though number 48 fuse witch gave me 13vdc. I don't have a schematic and not sure if any volts would be present on number 8 if the 4x4 isn't turned on or the tccm? I Also checked the connections to the tc motor and all looks good. Then again if i really do have a bad tccm and the 2 i tried at the junk yard were bad.....well my luck sucks then lol???

the roadie
09-10-2011, 07:09 PM
...Any one know how much voltage is going though the number 8 fuse? ...Front fuse #8 (you didn't specify front or rear so I have to say front) is powered by constant battery power. It should be hot on both sides at all times. Rear fuse #48 is powered by the RUN mode bus only off the ignition switch.

You may have a TCCM communication wire fault, but the lack of ANY lights on the mode switch points to a lack of power or ground on the TCCM. I'd be checking the voltages on the various wires of the TCCM connectors.

http://forums.trailvoy.com/attachment.php?attachmentid=8564&stc=1&d=1260831581

http://forums.trailvoy.com/attachment.php?attachmentid=8565&stc=1&thumb=1&d=1260831581

Dave_Stumph
09-10-2011, 08:24 PM
You sir are awsome!! Seems that I have more then 1 issue. First issue is my 0vdc on fuse 8 (both sides). Gona tackle that tomorrow and post back results


Edit: so I checked my 0vdc on fuse 8 in the front. Rookie mistake and metered to positive. Hence my 0vdc. That's all good. 12vdc present on fuse 8 :). Got into the tccm and check power going in on Orange wire and that's 12vdc. That's all good. Then I went to the tccm switch and I gots power coming in on brown wire at 12vdc. I also checked the LEDs to make sure they were not burnt out so I grounded each out separately and they all light up. So I'm at a loss?? I have 5vdc on my reference points and the switch meters out fine.?? It's prolly soothing I've over looked or it's something that the dealer might have to look into? I'll post back if anything changes?
Feel free to steer me in any directions :)

NYDeer
11-16-2011, 05:21 PM
Going to swap TCCM & report back.

In a bind for time, & couldn't find a used TCCM to try, so I took it to the Stealership for diagnosis, & estimate before repair.

2hr diagnosis/ install new TCCM, & flash TCCM, Drumroll please.... $612 + TAX!

Questioned how they knew for sure, service manager said it was definitively the TCCM, no codes for anything else, & will function perfect with new TCCM. Said 'No Thanks'! Paid 1hr labor for diagnosis, picked up and found a used '03 TCCM 45 mins away for $75. Ten minutes, and 4WD is fully functional again!

Thanks Trailvoy!

the roadie
11-16-2011, 05:42 PM
... I took it to the Stealership ...Sigh...:sadcry:

Any of a hundred members here could have diagnosed your symptoms with a 2002 TCCM in ten seconds.

That your dealer couldn't or wouldn't do it in the same time for the same cost as here (zero) speaks volumes about their process-driven greed. And now you've changed it you know it's not an hour labor to swap one out, either. :hissy:

$612 isn't quite ten times your cost of $75, but TCCMs used to be cheaper until the junkyards caught wind of the GM misdesign for 2002 units and started jacking up their prices. You used to be able to get them for $25.

rpog80
11-24-2011, 01:16 AM
Just logged in to report on my story to get our 02 Envoy 4WD back.

Have an 02 that sat for 9 days when we were away on vacation, Came back and the battery was so dead, there wasn't enough juice to remove the key from the ignition when it didn't start. Had it jump started - the "Service 4WD" light came on immediately when the car started. So I came here to read up - tried the "pull fuse 8" to wake up the TCCM, didn't work - tried the "hold 4WD switch past the 4LO position", didn't work.

So following the wisdom written here, I called the bone yard to see if they had a TCCM - I was in luck, they had an 03 TB, $75 for them to pull it and $50 if I pulled it myself. Was the easiest $25 I every saved, the TB that I was to pull the TCCM from already had the dash panels and column removed - took all of 30 secs to unplug the TCCM. Got home and removed the 6 screws holding on the 2 dash panels below the column - reached up behind/below the headlight switch and pulled the TCCM and its little plastic holder out from underneath the metal dash frame - removed the 3 plug connections on the TCCM and popped in the one from the bone yard - put the dash panels back on - entire job took 14 minutes. The "Service 4WD" light was out, the lights on the 4WD selector were back on and the 4WD worked fine.

As noted in other posts, the model number on my 02 TCCM was 15085386 and the 03 TCCM was 12580060.

Thanks for the wisdom provided on this site!

jcjarhead
11-30-2011, 04:10 PM
I have read the multitude of threads on our TCCMs. I still have a couple of questions I want to put out there before I make a move on a replacement (used one from a junk yard per Roadies advice on not needing reprogramming.)

1. It's an 04 TCCM which means it should be the updated one less inclinded to fail?
2. Is my TCCM about to go? Should I simply spend the $90 (with ship) and replace it; as I will need reliable 4HI (I dont use the A4WD as per Roadie rules) in the Maine winter (although it has been shocking warm of late)

I have serviced the transfer case as suggested in the Owners Manual and used dealer purchased Autotrac fluid. Lately my indicator lights on the switch sometimes do not illuminate at all? This is intermittent as I just went out for coffee and sure enough...worked fine? I also engage the selector to see if I could hear the actuator moving.....I could. I have also done the switch the switch a 100x thing to see if it helped....it didn't as the lights are still hit or miss.

I am tempted to just spend the $90 and be done with it...but of course wanted to bounce it off the forum first for any addtional insights. And to be sure I am addressing the likely cause. THANKS TO ALL in advance!

the roadie
11-30-2011, 06:10 PM
...It's an 04 TCCM which means it should be the updated one less inclinded to fail?...Lately my indicator lights on the switch sometimes do not illuminate at all? ...I also engage the selector to see if I could hear the actuator moving.....I could. ...Only 2002 were really flaky and failed a lot. Your 03 is not as likely to die.

If your switch lights are out, but the functional test is fine, and your encoder motor AND front axle actuator are working and making noise when expected in each mode transition, then you may have just a bad light circuit.

When the lights go out, do you get expected mode transitions?

You could have a flaky PU/WH wire that drives the dimmable LED lights only. The big question is: Do the lights all flash at once when you turn the ignition on during the lamp test?

http://forums.trailvoy.com/attachment.php?attachmentid=7659&d=1257465176

jcjarhead
11-30-2011, 08:19 PM
1. Functional test. Yes, all switch lights and gauge lights on at startup.
2. Encoder motor. I can hear it activating in the rear.
3. FA actuator. Not sure if I hear or feel it when lights are out.
4. Expected mode transitions. I am not sure it is engaging when the lights are out? The switch lights do blink between transitions and it does feel engaged when switch lights are on.

Hopefully I have given you enough information to advise if my TCCM "sleeps with the fishes?"

the roadie
11-30-2011, 10:22 PM
How often are the lights dark on you?

You say they are all on during the lamp test time, and then go dark later?

When they are dark, you can hear the transfer case encoder motor whine during mode transitions?

The FA actuator ONLY makes a noise (higher pitched) during 2HI->A4WD transitions and A4WD->2HI. You should be able to hear its noise superimposed on the encoder motor for those two transitions only.

When you say the switch lights blink during transitions, then I'm not clear on WHEN the lights go dark unexpectedly.

jcjarhead
12-01-2011, 09:37 AM
I will attempt to give you more detail in my responses; why be slave to brevity? Especially when it leads to confused: Sorry I was way loose with jumping around on timeframes in my response.

How often are the lights dark? lately it seems to be about 30% of the time...but it could also be some observational bias as I have started to watch for the lack of lights now that I have seen it happening.

On during lamp test, and then go dark later? I need to observe this more...I will be sure to take note each time I start up and record what happens when I see the switch lights are out. I had not been noting it so closely prior to reading the posts after I noticed the condition. Everything was normal on the drive in this am.

When dark, is tc encoder motor whining? Yes...I believe that is the sound coming from the TC in the rear?

Is FA actuator engaging? It appears to be working when conditions are normal....I need to take better note when the abnormal condition reappears. I was unsure I heard/felt it last time I was trying to test in abnormal mode. I will use your 2HI to A4WD and back procedure next time I observe abnormal conditions.

When are lights going dark during transitions? Sorry...very poorly worded. I am unsure when it is they go dark....not sure if they did go thru lamp test as above. I was already underway when I first noticed the condition. I will be sure to do a better job of dx when in the abnormal condition as I am more carefully watching the lamp test now.

In the normal mode...the quick blinking between transitions was present if that helps. Then the switch lights were on as normal.

Thanks for all the insights Roadie! I will be sure to report back when more data is available. I appreciate your constant gentle pressure pushing me in the direction of a coherent response to your questions. I need that kind of editing!:)

the roadie
12-01-2011, 01:50 PM
... I appreciate your constant gentle pressure pushing me in the direction of a coherent response to your questions. I need that kind of editing!:)THink of me as Dr. Gregory House, MD - but for systems, not people. In my day job, I'm often a diagnostician for million dollar semiconductor test systems. Not easy to get them to cough up their symptoms like a human can.

I even wrote this essay a few years ago in case anybody's interested in structured troubleshooting tactics.

http://www.roadie.org/bill%20carton%27s%2016%20rules%20.pdf

jcjarhead
12-01-2011, 02:15 PM
Now that is one well thought out document!:hail: I wish I were more of a linear thinker sometimes. Needless to say I work in sales so my enthusiasm gets the best of me at times and I go short on detail!:yes:

Your timing is spot on. I just went to drive to lunch and meet my 22yo son and guess what?....cluster lights were normal....but no lights at all on the switch lights...either at startup or thereafter. I also did the 2Hi to A4WD test several times while moving at low speed thru the parking lot upon my return....I could neither hear nor feel anything? From either the front or back?

Should I order the 04 TCCM from the junkyard ($88 with ship)? From reading the posts I assume as long as it didn't come from a Bravada I am good? It says it came out of a TB. Or am I way off base?

the roadie
12-01-2011, 02:42 PM
Or pull out your voltmeter and check the voltages at the back of the switch and the TCCM. You should also pull off and reseat the connectors to eliminate common oxidation as a cause. You *do* have a meter, don't you?

TCCM could be a waste of $$. I'd look for a local trailvoy buddy to swap with first.

jcjarhead
12-01-2011, 02:48 PM
I was half expecting to see a sarc icon after the voltameter question!:laugh: I am pretty limited in both tools and talent. I dont have one...but I know they are fairly inexpensive for basic models.....I will buy one and google how to use it...and advise....it would be great if it were the switch as that appears to be the least pricey part at about $30.

ttiger
12-03-2011, 12:16 AM
I purchased my TCCM from GM Parts Direct. It cost about $200 Shipped.

Here is how you replace it.

First take off the panel under the steering wheel and the pannel that is below that
http://i7.photobucket.com/albums/y276/jefftheGRAFF/Trailblazer/TCCM005.jpg


This is what you will see from under neath the blue clip goes into the TCCM there are 3 different plugs that clip in there. It is right behind the metal plate that you will see when you take off the pannel, It is all the way to the drivers side.
http://i7.photobucket.com/albums/y276/jefftheGRAFF/Trailblazer/TCCM001.jpg

These are the 3 plugs after you take them out of the TCCM They unclip pretty easily but require a little contortion to get your hand up there to them. I am sure you could just take more stuff off but this wasnt too bad.

http://i7.photobucket.com/albums/y276/jefftheGRAFF/Trailblazer/TCCM002.jpg

This is how they go in the TCCM. Note, you cannot put them in before you pop the new TCCM into its bracket. This is just so you can see the order of the plugs because you won't be able to read the label on the TCCM when you put it into place.

http://i7.photobucket.com/albums/y276/jefftheGRAFF/Trailblazer/TCCM003.jpg

Clip the TCCM into its bracket, and install the plugs. The small black plug goes all the way to the passenger side, I labeled them in the drawing.

http://i7.photobucket.com/albums/y276/jefftheGRAFF/Trailblazer/TCCM004.jpg

Put the dash back together, go to the dealer and get it programed.


any questions just ask here, don't PM me


could you repost photos?

the roadie
12-03-2011, 03:19 PM
could you repost photos?Since the original poster hasn't been back to the site in a long time, I suspect not. Sorry.

Last Activity: 12-27-2009 04:48 PM

Somebody will have to take new pics.

qbmike
12-13-2011, 01:40 PM
Roadie ,

Thanks for the help, even though I never asked directly.

This information you may find interesting..

I had a 2003 trailblazer with no-lights-on-knob, (only briefly when you first turn on the key). Also the same ;"Service 4 wheel drive" light turned on, on the dash. Yes, I said 2003.. I fixed by replacing the TCCM with a 2004. I wonder if they didn't put "leftovers" from 2002 in this truck.. The OLD/BAD unit's part number is 12580060.

This is the part number of the replacement TCCM that appears to work fine; "12588290".

Now...

I have 30 years of electronics experience and with one look at the "heat sink" (the aluminum piece with the fins on it), I could tell that it wasn't built heavy enough to run the transfer case shift motor. Besides this, when I took the box apart, I seen the worst sink-job that I have ever seen. The only way the controller ICs could sink ANY of the heat is THROUGH THE PC BOARD!!! (and through the paint and other coatings and a cardboard-like layer between the heat-sink and the PC board!)They may as well not bothered attaching a heat-sink at all. If they would have put the heat-sink on the OTHER SIDE on top of the ICs , it may have worked, but even then, the heat-sink that is there doesn't look like it would cool those chips while they are driving the shift motor at a 0 degrees when the motor and transfer case oil is very stiff. You might also think that hey, its cold out, it don't need as much heat sinking then, but this box is inside the passenger compartment next to heat ducts and worse, under the hottest part of a vehicle when the sun is shining..

I am sorry to say , but my 6 year old cold have come up with a better design!

Budd1470
12-21-2011, 04:34 PM
Does anyone have GM Parts direct part # for that 03 TCCM? Thanks in advance.
Its a Trailblazer EXT by the way.

Nozzleman
12-21-2011, 04:44 PM
From past experience, you can't beat LKQ for the part, If you don't absolutely need a NEW part. There are plenty of recyclable modules floating around. In my case, I found that it wasn't the module but a wiring issue. I now have a $35 module standing by. How much is a new one?

Budd1470
12-21-2011, 04:47 PM
I did a search on gmpartsdirect and this #12588290 did not come up. Is there a new # for the TCCM?
Thanks

Ramsey45
02-05-2012, 08:59 PM
I own a 2002 and 2003 Envoy. Had a bad TCCM in my 2002 and now have a messed up Transfer case disconnect on my 2003. Needed to get 4wd working for my wife or would be in the new car market. Good news is I was able to take the TCCM from the 2003 and put it into the 2002. Seems to be working fine.

Does anyone know if there is a need to get it flashed? Any issue with the two cars having different gear ratios?

tinman12
02-17-2012, 05:10 PM
Does anyone have an updated link to the pictures of the location of the TCCM and how to replace it?
Thanks

cntinuum
02-17-2012, 05:24 PM
I did a search on gmpartsdirect and this #12588290 did not come up. Is there a new # for the TCCM?
Thanks
For what its worth, this is the number I have 12590220. I see ebay auctions with this part number. Check out the list in this auction for x-fer.
http://www.ebay.com/itm/TCCM-4WD-TRANSFER-CASE-CONTROL-MODULE-COMPUTER-CHEVY-TRAILBLAZER-EXT-GMC-ENVOY-/120845882625?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%26itu%3DUA%26o tn%3D5%26pmod%3D270809641104%26ps%3D63%26clkid%3D6 400447629337217796
eBay item 120845882625

cntinuum
02-17-2012, 05:33 PM
Does anyone have an updated link to the pictures of the location of the TCCM and how to replace it?
Thanks
A lot of the content on this site has moved to another site. There is a dispute going on. This site changes the URL to point to TrailVoy and will not allow me to tell you where it is at. Might want to search for GM and then the word Nation with a dot and then the suffix COM.
I would go there and look. If no pictures, the guru's that posted it "live" on the site I suggested.

Map709
08-31-2013, 04:49 PM
I know this post is super old but does anyone still have these images? I'm in the process of trying to replace my TCCM. Thanks!

cntinuum
08-31-2013, 06:42 PM
I know this post is super old but does anyone still have these images? I'm in the process of trying to replace my TCCM. Thanks!Did you read the previous post? Taking the inspection panel off the side of the dash was a MAJOR help to me in seeing the TCCM and getting it clipped back into place.

The forum GM t nation . com has a wealth of information and is the best group of guys on the Trailblazer. This is where the content got moved to.

Robthemac
12-14-2013, 11:33 PM
There are a couple of threads about this issue, and Ive found this site very helpful. My 02 Trailblazer had no indicator lights on the 4wd switch and no service 4wd light on. I trusted my online research and bought a working tccm from a wrecked 03 Trailblazer on ebay for $80. I installed it myself and it worked like a charm. 4wd switch works great!! No programming necessary. The hardest part was holding the new one in place and simultaneously plugging the wires in with the limited access. Bloody knuckles on both hands, but they feel fantastic because 4wd is working as we get our first snow storm of the year in the Boston area. This website was a big help! Thank you!

LowSlow O FO
01-15-2014, 02:20 PM
Thanks for the extensive T/S info. Roadie the schematic was priceless. You guys make owning this vehicle much easier.
No selector switch light. Blown fuse. reset connectors at TCCM replaced fuse. Blew another fuse (nbr 8) 30 amp. Replaced TCCM (got off EBay) also unsnapped fuse block shook down wiring suspecting possible chafing causing ground . Installed new fuse . Ops cks ok .
Oh yea I did remove the plug at xsfer case motor earlier before blowing another fuse so I decided the motor not to be cause . Next up change xfer case oil . Seen it mentioned enough to see the error of my ways.

ttiger
01-15-2014, 10:16 PM
well i crash my TB , now i'un the unhappy owner of a toyota cellica.. ill buy another TB as soon as i can..

redsride
03-18-2014, 09:50 PM
Moved to the proper forum.

patrickj75
11-23-2014, 10:54 PM
I just installed a new TCCM in my 04 Trailblazer and now the lights on my switch don't light up. Does that mean I need my reprogrammed or do I have another issue?