Location of Auxiliary Brake Control Harness/Wire U86 Option - keywords connector lamp light locate trailer

This PI was superseded to update model years. Please discard PIT3479C.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Owners may question the location of the blunt cut Auxiliary Brake Controller Wiring Harness RPO U86.

This harness runs from the rear 7-way trailer connector to just after connector C126 and ends. The Dk Blue blunt cut wire (Circuit 47) is taped to the harness (shown below).

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.