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 default actions for C0321 may set C0306.
EL-49741 harnessis a good source for 9 V.
EL-49742 harnessis a good source for B+ and ground.
The transfer case drain plug is a good source for ground.