Drivetrain - 4WD Light ON/4WD Inoperative/DTC C0550
TSB SB05-05-S001Service 4WD Light ON, 4WD Inoperative, Harsh
Engagement of 4WD, No Communication with TCCM,
DTC C0550 Set
ISSUE DATE: FEBRUARY 2005
Affected Vehicles
2004 Isuzu Ascender (US/UT) Models with NVG 226 Two-Speed Transfer Case
Service Information
Condition:
Some customers may comment that the Service 4WD light is on or that the vehicle's 4WD is inoperative. Others may comment on a harsh engagement of the 4WD system. Transfer Case Control Module (TCCM) diagnostic trouble code (DTC) C0550 may be set. Also, there may be no communication with the TCCM.
Correction:
Important:
This Technical Service Bulletin ONLY applies to the 2004 model year vehicles listed above with TCCM DTC C0550.
Follow Service Procedure.
Service Procedure
1. Install a scan tool and attempt to read the TCCM DTCs.
^ If there is NO communication with the TCCM, continue with the next step.
^ If there is communication with the TCCM and DTC C0550 is present, continue with step 8.
2. Turn the key to the OFF position.
3. Open the hood.
4. Remove the underhood fuse block cover.
5. Remove the ATC fuse for 30 seconds.
6. Reinstall the ATC fuse, reinstall the underhood fuse block cover and close the hood.
7. Attempt to communicate with the TCCM with a scan tool.
^ If you are still unable to communicate with the TCCM, refer to Diagnostic System Check - Transfer Case in the Service Manual.
^ If you are able to communicate, continue with the next step.
8. With a scan tool, check for TCCM DTC C0550.
^ If other DTCs are present, refer to Diagnostic Trouble Code (DTC) List in the Service Manual.
^ If TCCM DTC C0550 is the only code present, clear the code and continue with the next step.
Reprogram the TCCM with a new service calibration released with ITCS CD version 32 or newer.
Refer to Service Programming System (SPS) in the Service Manual. As always, make sure your TECH2(R) is updated with the latest software version.
9. Refer to Transfer Case Control Module Reprogramming in the Service Manual.
10. Road test the vehicle.
Warranty Claim Information
Use the labor operation shown.
Disclaimer