4wd not workin

[02dubduce]

i know weve talked about it before. but since upstate ny has anywhere from 2.5-8ft of snow, i talked to my dealer about my 4wd issue. my 4wd does not work the electronic switch doesnt work either. the dealer (small, local dealer) said 4wd not working can be an issue due to not using it, he said sometimes itll freeze up and mechanics will tap the small 4wd engaging motor with a hammer while someone tries using the toggle switch. im just courious is anyone knows of this method or has come across similar issues. i do plan on bringing it to his mechanic but with the massive amounts of snow he might be booked up,

[Mean_I-Sixer]

Mine did simmilar things, no lights on the selector in the cab. No 4x4!!
I pulled the fuse out that is located under the hood marked ADC, or something similar, for about 10 sec. then reinstalled it. Been working great ever since.:m2:

Can't hurt to try and its a free fix:thumbsup:

[02dubduce]

i looked and couldnt find it where is this adc fuse located? mines an 02 if it makes any difference

[dtown]

I just disconnected my battery for about 30 seconds, reconnected and haven't had any problems since.

[Mean_I-Sixer]

Its fuse number 8, 25 amp. My fuse is beige in color. Its located in the fuse center, a black box behind the battery and to the side of the brake fluid resovoir. Take the first cover off, turn over find #8 ATC, just pull up on the second cover and it will come off. Remove fuse then replace. Any trouble, let me know.

[02dubduce]

got the fuse out, waited 60 seconds tried it. toggled the switch a few times once in the car, 4wd service light came on, i guess at least i know the switch isnt broke, the lights flashed on them

[Mean_I-Sixer]

Good to hear! Some progress. Try 4lo and see if the 4x4 is working. My switch lit up and has been working fine after that.

[02dubduce]

ill see what i can come up with, have you herd of it freezing up from not using it?

[Mean_I-Sixer]

nope, cant say i have

[02dubduce]

noticed something new, after fukn with the switch all day the 4wd toggle switch lit up with a red "n" any ideas as to what that is?

[rmac694203]

I think you may have put the transfer case in neutral. It's for when you're towing the truck with another. I've never done it, but think it's engaged when you push the switch all the way to the right and hold it. Someone else should chime in though and verify this.

[titanium10k]

If you is acting properly and the N is lit then you are in neutral. But be careful because even if you truck is in park it can still roll. Set that parking brake. But because you have been having 4x4 problems its probably still got problems. There are quite a few steps to do to get into neutral. There is plenty of info in the manual on proper 4x4 shifting procedure.

[Gm Tech2]

Guys there is an updated program for the TCCM - what is happening is the transfercase module is not wakeing from sleep mode

[clr114]

How much is the update on the TC? Do all dealers have access to it? I'm planning on taking mine in for some routine service and inspection soon, might as well get that done too ... if it doesn't cost too much.

[Lmhsdaddy]

Guys there is an updated program for the TCCM - what is happening is the transfercase module is not wakeing from sleep mode
Funny you should bring that up! My '03 was shifting oddly so I took it in for service. The dealer told me that there was a program upgrade and installed it free. After that my service 4WD light that had come on every now and then hasn't come on since.

[geyer]

I have the same problem with 4wd and the N light comes on sometimes. Also driver door controls sometimes are dead for days and then work days. One more thing, the 1,2,3 on the heater fan doesn't work. I'm sure this is all connected somehow. It's been driving me crazy for a month. Mine's an 02.

[RozmerJJ]

I have the same problem with 4wd and the N light comes on sometimes. Also driver door controls sometimes are dead for days and then work days. One more thing, the 1,2,3 on the heater fan doesn't work. I'm sure this is all connected somehow. It's been driving me crazy for a month. Mine's an 02.

The 1-2-3 on the heater fan is most likely the blower motor resistor pack. This is a cheap part and a very easy DIY fix. Just search for Blower Motor Resistor and you will find the steps needed.

For the Door controls I would check the connector in the door hinge area, unplug it look at the contacts and make sure it is clean and dry then plug it back in.

The 4wd problem could just be a bad selector switch but I'm not 100% sure on this.

[geyer]

Odd thing is this all started happening at the same time. Is there anything that is common to all the problems? I have a Haynes manual but the schematics aren't too easy to follow. Thanks.

[RozmerJJ]

As far as I know there is nothing common to all the systems you are having issues with. I think it is just bad luck, even if the BCM was failing I don't think that would affect the blower motor.

[flyinhawaiian]

The service 4wd came on and 1st thing I thought was check Trailvoy. I came home and found the fuse to pull #8 under the hood (I left it out for about 30 sec. now "no light and no more problems".
Thanks:woohoo:

[Doc Brown]

There are at least 8 TSBs related to the crappy electronics for the 4WD. Your problem is probably one of them. My TB just cost me a grand getting this crap fixed. I love my TB, but I really hate the 4WD. Its given me nothing but grief. The unfortunate part of this is that I know of no way to read the DTC codes without taking it to a dealer. I've been trying to find out if other machines at small shops can read them, or if there is a small one just for the TB that I could buy. It'd be worth it to diagonose this stuff myself.

1) Look at the wiring going to the transfer case, see what condition its in. If the casing's are cracked you'll have to replace those sensors at the very least (they are speed sensors, $51 each), you'll also have to replace the wiring and plugs. This one's been know about since '02 and applies to every TB w/4WD built since then. (TSB 06-04-21-001, TSB 05-04-21-003B)

2) The actuator/encoder can go bad as mine did. Very expensive, over $500 just for the part. 2 related TSBs (TSB 04-04-21-004, TSB 02-04-21-008A).

3) TCCM. Sometimes they can be reprogramed, sometimes they need to be replaced. Mine had to be replaced right after I bought it 2 years ago. I think the cost for the unit is about $400. Its inside the dashboard behind the cluster. If it gets replaced, it has to be reflashed with the latest code. 6 TSBs related to this item alone (02-04-21-006E, 05-04-21-002, 04-04-21-004, 04-04-21-001, 03-04-21-005, 02-04-21-008A)

4) Its very common for the selector switch to flake out (TSB 02-04-21-002A)

[BBK]

I replaced the selector switch...it seems to be working fine now, but I will inquire at the dealer for a TCCM update programming.

Thanks:tiphat

[crnarukam]

I love this site i joined today for some audio questions and said let me see if i can find whats wrong with my 4x4 i just ran out at 1130pm to try the fuse and worked like a charm had the problem for 5 months and went to 2 mechanics tryn to avoid the dealer, changed the switch hooked it up to the gm computer nothing helped this did it


-TY

[BlueTrail]

Its fuse number 8, 25 amp. My fuse is beige in color. Its located in the fuse center, a black box behind the battery and to the side of the brake fluid resovoir. Take the first cover off, turn over find #8 ATC, just pull up on the second cover and it will come off. Remove fuse then replace. Any trouble, let me know.

i just got my TB and this happen to me and you fixed it

[OnVoyEr]

hi guys, ive been looking into this problem, my 4x4 is not responding at all, no lights in dash or on switch, i pulled the ATC fuse and reset the battery and no change, the previous owner said he was driving and accidentally turned that switch instead of the rear wiper switch, the truck sort of took a dive and he quickly switched back to 2 hi. ever since its been dead, he had the t-case checked and it seems to be fine but it will not work. BTW mines an 02 SLE

[the roadie]

Was the fuse OK, and not open? Can you ohm it out with a meter? No lights at all is very suspicious of a power problem or a dead TCCM.

The Service 4WD idiot light isn't lit on the gauge cluster either?

[OnVoyEr]

i never tested it with a meter but the fuse is ok, and no light in guage cluster, when i get back from work in 2 weeks Ill take it to the dealer and see if they may need to "wake it up" with a software config, other than that it definatley seems electrical, TCCM is a good possibility too. thanks for the insight!

[CRoberts]

Mine did simmilar things, no lights on the selector in the cab. No 4x4!!
I pulled the fuse out that is located under the hood marked ADC, or something similar, for about 10 sec. then reinstalled it. Been working great ever since.:m2:

Can't hurt to try and its a free fix:thumbsup:

Fixed mine, thanks, mine is used about every other day i was about to go crazy without it

[nojamin]

have an 02 myself had same problem. the n means you got the transfer case in neutral. but my problem was the tcase actuator and had to be replaced

[YankeeRebel]

02 Trailblazer LTZ 4x4. Just installed a new dash switch. Changed t-case oil with the correct GM Autotrack-2. When operated in extreme cold (-10 and lower), service 4x4 light comes on, and switch either doesn't light up, or only does 2 high. Any ideas before I set this slut on fire?

[the roadie]

I would guess congealed grease in the front axle actuator slows it down, then it fails to move fast enough to satisfy the TCCM, which then sets the light. The grease is all over the gear train internal to the actuator.

http://forums.trailvoy.com/showthread.php?t=46356

Not sure if it's fixable. You might try to leave it in A4WD when it's warm. Then the only thing that has to move if you need 4HI is the transfer case encoder motor, which has a bit larger motor inside. No great harm running around in A4WD if it's that cold and you may meet snow or ice.

[zooy]

OK, my speedometer was acting up, so I decided to replace the speed sensor. (are there two on the transfer case? I saw 'em both, but didn't know if one was a different type of sensor. Just a sidenote, anyhow)

After replacing a speed sensor, wouldn't you know it, I lost 4WD. AND, it just happened to be my lucky day, I was in 4LO at the time, and now my front axle isn't engaging. So I find myself today in 2LO. A little research brought me here to this great forum (why didn't I find it sooner!), in which I realized the common four wheel drive issues these trucks have. So I was wondering if anyone had any insight on what happened during this simple sensor swap. Everything seemed to work great before; now the 4WD selector lights on the dash selector cycle at start up, then no lights on the switch, and the service 4WD lights up on the dash. I have tried pulling the fuse (which is good BTW), pulling the negative battery cable for a couple hours, rapping on the transfer case gear selector motor (is this what it's called?) while switching modes on the dash to no avail. Is my TCCM not waking up like I seem to have read? I have had this '04 TrailBlazer LS only a few months, so I don't know if it has the latest update for the TCCM. Anything else I can try before taking it to the shop or (gasp) the dealership?

Thanks in advance!

[the roadie]

Welcome zooy. Sorry to meet under these circumstances, though. The TC gear selector motor is called the "encoder motor" because of the encoder feedback function that reports back to the TCCM what position the motor ends up being at after it's commanded to move.

If your TCCM never woke up I don't think it would go through its turn-on diagnostic routine, but I think you really need a good independent mechanic with a scan tool that can talk to the TCCM and get some data out of it. Or the dealer.

Reseating the connectors on the encoder motor, the front axle actuator, and the TCCM, and inspecting the wiring as much as you can see of it, may be all you can try without calling in the big guns.

What made you suspect the TC speed sensor rather than the dashboard gauge servo motor on the speedometer display? Did you also lose the cruise control function?

[zooy]

Does the cycling of the lights on the switch indicate the TCCM is going through its turn-on diagnostic routine? Or are you refering to the Service 4WD light? I am just trying to go to the service shop with as much info as I can!

Well, I replaced the TC speed sensor after talking to my father-in-law, who is a really good mechanic, but hasn't worked on this type of vehicle before. I guess he probably didn't consider the gauge servo motor. My cruise was still working BTW, so I'm guessing I was probably barking up the wrong tree.

I'll check the wiring, re-seat the connectors, etc. you recommended before consulting a shop/dealership.

Also, I got a hold of a crude code reader that spit out some weird codes no one (including google) had ever heard of. Besides the AIR pump code that has been there since I bought the truck, there were the following codes:
0410 (pretty sure this is the AIR system)
8107
6d00
1A00

Any insight on these? I'll come back with what I find out, what worked, etc. Thanks for the help!

[chuckek]

The red N means the transfer case is in neutral. Owners manual tells the steps to disengage or (reengage) transfercase. However I got my Red N to go off but the 4wd still is not working Mechanic told me it could be the shift control module.

[zooy]

Well, I took the TrailBlazer to the shop, and they determined that it's the encoder motor position sensor that has gone bad. I am having trouble finding one online. They can get me one for $160, but since I said I'm going to install it myself, they recommended I purchase it elsewhere to avoid their markup. Is this a straightforward install? I live in an apartment complex and don't even have a jack, but I have seen where the encoder motor is and think I can get to it fairly easy. But since it's pretty snowy here in NY I was thinking about just having them install it since they said it should only take an hour. I'd be saving $55 in labor, plus the markup on the part; they'd probably let me buy it elsewhere and have them install it, but I didn't ask. Whaddya think? Thanks!