Diagnostic Aids

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.

The transfer case drain plug provides a good ground point.
The EL-49742 harnessprovides a good source for 12 V and ground.
Inspect the rear internal gear teeth for damage.
Visually inspect the VSS for cracks or damage.
Ensure the VSS is properly torqued to the transfer case housing.
This diagnostic relates to the VSS located in the transfer case and not the OSS located within the transmission.