Service 4WD Light

[2002BlkLTZ]

Anyone have access to or know the TSB number for the Service 4WD light problem on a 2002 Trailblazer? I don't feel like paying for the alldatadiy service, and can't find the TSB anywhere else. Anyone have any idea if the dash switch is the cause of this intermittent problem? (light comes on, and indicators over the switch do not work).

[04TBEXT]

Is you vehicle a 2WD or 4WD?...just kidding. I find (3) TSBs regarding "4WD" light on condition for an '02 T/B. 04-04-21-004, 02-04-21-006D, and 02-04-21-002A. Good luck..

[Blulytes]

beat me to it...

[2002BlkLTZ]

Thanks for the numbers! I know there's some on here who have access to them, just wondering if anyone's got any of those TSB's they can send my way? I'd be SOOO glad. The truck, the last two mornings, and once last week, has been showing "service 4wd" upon starting it. No matter how many restarts, light stays on, and indicators over switch (little orange lights) aren't lit. I get to work and park, by lunch, problem's solved :confused: It has been cooler the last couple mornings here, and not as humid, wondering if that's related to it? :undecided Anyone else had this problem, it seems to be a common GM problem, not just with this platform either. Thinking of replacing the switch, I think I found it on gmpartsdirect for 30 shipped. I have extended warranty, but I got it with a $200 deductible and I think I can probably fix it for less than that, long as the whole transfer case isn't shot! :duh:

[bmm354]

NOTE: I will remove the full text of these bulletins within 24 hrs. I was able to find these:

Service 4WD Indicator Illuminated, DTC B2725 Set, Transfer Case Selector Switch is in One Position - Indicator Lamp Indicates Another Range Is Selected (Replace Transfer Case Shift Control Switch) #02-04-21-002A - (02/11/2003)

Part Number 15194913
Switch, Transfer Case Shift Control
Qty 1

---------------------
and...

Inoperative 4WD/AWD Lamps, Inoperative 4WD/AWD System (Reprogram Transfer Case Control Module) #02-04-21-006B - (08/18/2003)
with Electronic Shift or Active Transfer Case (RPO NP1, NP4 or NP8)

Correction
Remove the underhood (ATCM or TREC) TCCM fuse.
Wait 30 seconds.
Reinstall the fuse. The module should "wake up" and communicate with the Tech 2®.
Check for codes in the TCCM. If a C0550 is found, replace the module and go to the next step.
Reprogram the TCCM using normal procedures...

---------------------

Try removing the fuse as per the 2nd TSB to see if that helps. Edit: You're right about this being common for other vehicles too... the 2nd TSB includes all 2002-03 GMT360/370s (TB, Envoy, Bravada) full-size pickups, and the Tahoe/Suburban too. Bascially anything w/ an electronic t-case.

[Blulytes]

By the way...

They are all listed in the resource section of the site!

http://www.trailvoy.com/index.php?page=resources

[2002BlkLTZ]

Freakin A! I had no idea they were all listed here :o You all are great, thanx for the help! Looks like I'll try the fuse pull, probably replace the switch, if none of that I'll try to get the control module updated! Hope that doesn't cost too much, or if it does it's over my deductible for my extended warranty!!! Maybe it won't go that far!

[bmm354]

I can get to the page w/ the TSBs, but it only shows a short blurb about what each TSB is and doesn't have repair info. Is there another page that has the full info?

BTW - I understand you can buy CDs off eBay with the full info, and some public libraries actually subscribe to the full AllData service for all vehicles.

[triz]

I have the same thing happen to me. Usually after a few starts it shuts off...very annoying.

[2002BlkLTZ]

Quick update to this thread, I've been waiting for my truck to do this again so I could try pulling the fuse and see if the control module "wakes up". This morning the truck had the above mentioned problem, I restarted twice to make sure the condition wouldn't disappear on its own. After pulling the fuse and restarting again, all was well. Looks like it may require the control module reflashed or replaced. I want to wait until it does it one more time to confirm pulling the fuse is what reset it. If extended warranty will cover it I'll get it replaced, if it won't, I guess it'll depend on the cost. I was hoping it'd be the $30 switch on the dash, but should've known better :duh: :cool:

[GusMan]

Which fuse did you pull? I just had this problem happen to me as well on my 03TB-EXT. I looked in the owners manual and found the fuse labeled "All wheel drive" or something like that. Fuse #8 on the underhood block. I pulled that fuse and the problem disappeared. I guess my question is that since I did that, I am wondering if lost any trouble codes for the dealer to look at? In any case, I am going to have the dealer look at it at the next oil change.

[2002BlkLTZ]

The fuse I pulled was number 8, I think, I'll have to confirm that after work. It was listed on my 02 as "ATC" I think. This leads me to believe it's a problem with the TCCM not "waking up" as described in the earlier TSB. It seems the cooler, damper mornings are when my truck's prone to this. A hot summer morning, where it's 80 by 9:00 seems to not have a problem.

[02GMC_ENVOY]

My 02 Envoy did the same thing I took it in and they replaced the switch and the TCCM and reprogrammed it. Cost the warranty company about $600 I think :rotfl: hope that helps.

Joe

[2002BlkLTZ]

Should have this problem fixed now, but OUCH! I should've done the fix myself. Turns out my TCCM couldn't just be reprogrammed, it had failed. The service guy at the dealership said a lot of the time, a reprogramming is all that's needed, to the tune of $78.00 at my dealership. Replacing the module cost me $414 plus tax at the stealership. Could've bought the module for $174 shipped off GMpartsdirect.com, I would've still owed the dealership for the diagnostic, which, suprisingly, would've cost me $78.00 (Hmmm, same as the reprogamming! What a crock). I *think* this module is also located under the rear seat, as whoever worked on my vehicle had cleared it off behind the drivers seat, as if he was working under there. Part number for the module, if anyone else has this problem, is 12590220, the trouble code GM got off the TCCM was C05501 - Failed Transfer Case Module.

**edit to add** I do not know if a new module (from GMPD) would then have to be programmed, which would add additional cost from the dealership.