Diagnostic Aids

WARNING: This page is about a different car, the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, and 2012 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 harness is a good source for 9 V.
EL-49742 harness is a good source for B+ and ground.
The transfer case drain plug is a good source for ground.