Diagnostic Aids
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
If there are any DTCs set for GMLAN communication such as U0100, U0121, U0140, or U2099, diagnose them first before to resolve DTCs described in this section.
When the TBCM ground is open circuit, in addition to setting DTC C1118, DTC C1116 and C1117 may also be cause these DTC to set. In this case, diagnose the TBCM ground first for open circuit fault before to diagnosing DTC C1118.
If there is an aftermarket trailer brake controller, the ITBC must be disconnected. Do not power both ITBC and aftermarket controllers to control the trailer brakes at the same time.