Test Description

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

3) - Tests whether the transfer case shift control module is sensing any change in all of the encoder channels.
4) - Helps determine whether the shift is prevented due to a mechanical fault.
5) - Tests whether the transfer case shift control module is sensing any change in any of the encoder channels.
6) - Tests if proper reference voltage is being supplied to the encoder from the suspect circuit.
7) - Helps determine whether a short between 2 or more encoder circuits exist.
8) - Helps determine whether the shift is prevented due to a mechanical fault.
9) - Tests for the electrical energizing of the encoder motor.
10) - Tests the suspect circuit(s) for an open or a short to power.
11) - Tests for short between the suspect circuits.

Fig 1: DTC C0387 Diagnosis (Steps 1-8)

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC C0387 Diagnosis (Steps 9-15)

Courtesy of GENERAL MOTORS CORP.