Avalanche Owners Zone > Problems: Recalls, Dealerships, TSB & Warranties

Service 4X4 TSB?


Can some please post TSB 02-04-21-006D March 04 AWD/4WD System- Lamps/Systems Inoperative?

borrowed from HERE ...

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).

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.

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 2ᆴ.

  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 2ᆴ.
  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.

Hired Gun:
Thanks this happened this morning to Jennifers 04.  I will print this and take it with me.  This site is so helpful. :wave:

I take it that TSB does not cover a Service 4wd light coming on intermittantly while the 4wd and lights still operate perfectly?

I also got this message this morning in Flagstaff AZ on the way back from Kansas ....heading home to Vegas. I had stopped to refuel, checked the manual and the key cycle reset everything.  Drove thru MAJOR rain storm in New Mexico on Hwy 40 less than 12 hours earlier.

I will also print this out for future reference.

Love this site... its almost better than food. 


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