Force Motor Circuit Check: Notes

WARNING: This page does not describe the selected car, but rather 24 other vehicles, including the 1992 GMC Yukon, 1992 GMC Vandura Special, 1992 GMC Vandura, 1992 GMC Value Van, and 1992 GMC Suburban. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: This flow chart requires the use of a bidirectional (Tech 1) scan tester.

The force motor is a PCM/TCM-controlled device used to regulate transmission line pressure. The PCM/TCM looks at TPS voltage, engine RPM, and other inputs to determine the appropriate line pressure for a given load, then regulates the pressure by applying a variable amperage to the force motor. The applied amperage varies from .1-1.1 amps.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Checks the PCM and TCM's ability to command the force motor.
Checks for voltage at PCM/TCM.
Checks internal transmission harness and force motor for low resistance.
Checks for short to ground.
Checks internal transmission harness and force motor for high resistance.