Wet Weather turns my 4x4 light on

[Newfy_Mike]

An issue I had was weak battery which first made this light turn on. I replaced the battery and the dealership told me I had to have my 4x4 reprogramed. Everything worked fine until the wet wheather came.

My 4x4 works. I have tried all modes on a nice day. But on a cold morning or wet day the light turns on.

If I drive for 15 minutes or so, then turn my Envoy off and on the light will turn off.

So I am thinking there is a grown fault issue somewhere

The dealership is saying I need to replace the transfer case control module

any ideas???

[KHill]

HAH replace the TCCM, that's a classic "up-sell" right there.

What you need to do is get the code and tell us what the car say is wrong with itself, from there we can troubleshoot a little more accurately.

[Newfy_Mike]

Thanks

The code is C0550 from what my paper work says.

But that is only when damp


and no i haven't

[KHill]

haven't what?

[KHill]

Woops, it looks like the dealer isn't lying this time (unless they made the code up)

Seems the C0550 is the suicide note from the TCCM...

Inoperative 4WD/AWD Lamps, Inoperative 4WD/AWD System (Reprogram Transfer
Case Control Module Using Labor Operation Code N8521) #02-04-21-006D - (Mar
24, 2004)
Inoperative 4WD/AWD Lamps, Inoperative 4WD/AWD System (Reprogram Transfer
Case Control Module Using Labor Operation Code N8521)

2004 Buick Rainier

2002-2004 Chevrolet TrailBlazer, TrailBlazer EXT

2003-2004 Chevrolet Avalanche, Silverado, Suburban, Tahoe

2002-2004 GMC Envoy, Envoy XL

2003-2004 GMC Sierra, Yukon, Yukon XL

2004 GMC Envoy XUV

2002-2004 Oldsmobile Bravada

with Electronic Shift or Active Transfer Case (RPOs NP1, NP4 or NP8)

This bulletin is being revised to add information to Step 5 of the
procedure. Please discard Corporate Bulletin Number 02-04-21-006C (Section
04 -- Driveline/Axle).

Condition
Some customers may comment that the 4WD/AWD indicator lights on the selector
switch do not work, or the 4WD/AWD system may be inoperative and/or the
service 4WD light is illuminated. The condition is typically intermittent
and always occurs at key-up.

Cause
The Transfer Case Control Module (TCCM) has not received the wake-up call
during key-up and has remained in the "sleep mode".

When the TCCM is in the "sleep mode", it will not communicate with the class
II bus or the Tech 2®.

Correction
1.. Try to communicate with the TCCM. If no communication, go to step 2.
If communication is possible, go to step 5.
2.. Remove the underhood (ATCM or TREC) TCCM fuse.
3.. Wait 30 seconds.
4.. Reinstall the fuse. The module should "wake up" and communicate with
the Tech 2®.
5.. Check for codes in the TCCM. If a C0550 is found current or in history
with or without other codes, replace the module and go to step 6.
6.. Reprogram the TCCM using normal SPS procedures, using TIS software
version 3 released March 8th, 2004 or newer.
7.. Verify operation and that no codes are present.

[Newfy_Mike]

even if it works some of the time?

On a dry day it works fine. I can put it into all 4 modes and works correctly. Just on cold mornings and wet days the light turns on.

So I am thinking there is a ground issue somewhere, maybe in the TCCM?

[KHill]

its possible that some water could be shorting out circuitry in the undercarriage. or computer components being affected by the cold. but here were on rather uncharted waters....


for some reason a TSB was written up saying that if there were ever this code in the TCCM that dealers are supposed to replace it. thats not a dealer trying to give you the shaft, but corporate GM covering it's ass, so something is usually wrong...

[clj3274]

last summer i drove through some water on the road .. 4x4 light started blinking and wouldnt work .. after a week or so of hot weather it went away.. now its back.. but from driving in wet road conditions ..when i got my oil changed they told me the little panel to get to oil filter was missing.. getting a new one.. its currently stuck in A4x4 .. when i try to switch it it just blinks and goes back to A4x4.. any thoughts on a fix that dont include going to the dealer .. dont want to get shafted by them

clj3274@vzw.blackberry.net

thx

[the roadie]

.... when i try to switch it it just blinks and goes back to A4x4.. any thoughts on a fix that dont include going to the dealer .. ...Put the switch in 2HI with the ignition off, then pull fuse #8 under the hood for 30 seconds, and put it back in. Turn the ignition switch to RUN but don't start the engine.

Describe fully the appearance of any lights on the switch or dash and any electric motor noises you hear from under the vehicle.

Change the mode switch to A4WD. Describe what happens.

Change to 4HI and do the same. Then A4WD again. Then 2HI.

Do you or a buddy own a meter and know how to use it if I describe some electrical troubleshooting?

[Newfy_Mike]

I will be back home Friday after a 5 month trip

But I will try your fault finding

I am good with electrical, hence being a tech

but I will give you my results sometime next week and get back to you

[Newfy_Mike]

Ok so when it is wet outside, I don't even get the amber light at the indicator selector for my 4x4

so nothing happens when I move the switch

but on a dry day or after I go for a long drive and turn the vehicle off and on, the light goes out on my dash and the amber light on the selector turns on.

I then have full use of my 4 wheel drive, I can feel it changing from 2hi, 4hi, 4low, 4awd

Since I have been back in town I seem to be having the same problem with my check engine light

And sometimes the ABS light with turn on, then the vehicle will rev a couple times before the engine shuts off

both problems are related to when it is cold and wet outside, so I am thinking I have ground issues, or maybe a new wiring harness is necessary

[KHill]

My guess would be water shorting. If you have access to a lift or chocks boost up your TB and look for shiny. It will be hard to find but there really isn't much wiring down under. When/if you find it, tape it or join it and hope that's all.