Diagnostic Aids

WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. 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.