Diagnostic Aids

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value.

Drive the vehicle if necessary to experience a fault.

If this DTC is present in a new vehicle, harsh shifting may occur since shift adaptive action is inhibited.

In certain applications, vehicle cruise control function may be used to verify if BUS circuit is operating properly. If this function is not operating, the engine controller may not be broadcasting a BUS circuit signal. This could be due to incorrect parameter setting at the ECU or a defective ECU. The vehicle OEM should be contacted to verify proper ECU setting.

Intermittent cycling of the TCC could indicate that a BUS circuit wiring problem exists. It is possible to have an open condition in the BUS circuit wiring and U2105 not set or only set when an open condition at the BUS circuit is present over the period of time needed to allow the U2105 to set.

It is necessary to have two 120-ohm resistors installed in the BUS circuit.