Test Description

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.

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

4. This step tests for voltage to the TCC PWM solenoid valve circuit at the 20-way connector.
6. This step tests the ability of the PCM and wiring to control the ground circuit.
10. This step tests the resistance of the TCC PWM solenoid valve and the internal wiring harness.

Fig 1: DTC P1860 (Steps 1 - 4)

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Fig 2: DTC P1860 (Steps 5 - 15)

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Fig 3: DTC P1860 (Steps 16 - 21)

Courtesy of GENERAL MOTORS CORP.