Diagnostic Aids

WARNING: This page is about a different car, the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, and 2018 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.

It is possible to have windings inside the motor shorted to the case resulting in a short to ground causing this DTC to set.
DTC C0306 54 may set when there is a brake fault.
DTC C0306 01, C0306 02 and C0306 04 may set when a loose connector or wire harness issue is present.
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.