Circuit/System Testing

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2011 GMC Yukon XL, 2011 GMC Yukon, 2011 Chevrolet Tahoe, 2011 Chevrolet Suburban, and 2011 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

Observe the 4WD Signal in the ECM Data List. The 4WD signal should display Enabled when you shift into 4WD and Disabled when you shift into 2WD.
- If the scan tool display does not match the transfer case range switch state, repair the transfer case system. Refer to Diagnostic System Check - Vehicle (with HP2) , Diagnostic System Check - Vehicle (without HP2) .
- If the scan tool matches the transfer case range switch state, continue with testing.
Program the ECM with the latest software version and retest for DTCs.
- If the DTC resets, replace the ECM.