Inoperative 4WD/AWD Lamps, Inoperative 4WD/AWD System, DTC C0550 Set, No Communication with TCCM (Reprogram Transfer Case Control Module) (VSS20020131)

Publication date: 2006-07-20
Reference number: VSS20020131
Supersedes refnos: 02-04-21-006, 02-04-21-006A, 02-04-21-006B, 02-04-21-006C, 02-04-21-006D, 02-04-21-006E, 03-04-21-006

Inoperative 4WD/AWD Lamps, Inoperative 4WD/AWD System, DTC C0550 Set, No Communication with TCCM (Reprogram Transfer Case Control Module)

TECHNICAL SERVICE BULLETIN

Reference Number(s): 02-04-21-006E, Date of Issue: July 20, 2006

Affected Model(s):	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)
Supercedes:	This bulletin is being revised to add Subject information and change the labor operation. This bulletin cancels and supersedes Bulletin Number 03-04-21-006. Please discard Corporate Bulletin Numbers 02-04-21-006D and 03-04-21-006 (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. Upon investigation, the technician may find DTC C0550 set.

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(R).

Correction

Try to communicate with the TCCM. If no communication, go to step 2. If communication is possible, go to step 5.
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(R).
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.
Reprogram the TCCM with the latest TIS software using normal SPS procedures.
Verify operation and that no codes are present.

IMPORTANT: For the 2002 model year, the TCCM must be replaced and reprogrammed.

Warranty Information

For vehicles repaired under warranty, use:

Warranty Information

Labor Operation	Description	Labor Time
K4121	Transfer Case Module - Reprogram with SPS	0.4 hr