Circuit Check - Force Motor

Force Motor Circuit:

Circuit Description:
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 line pressure appropriate for a given load, then regulates the pressure by applying a variable amperage to the force motor. The applied amperage varies from .1 to 1.1 amps.

The PCM/TCM then monitors the amperage at the return line and if the return amperage varies more than .16 amp from the commanded amperage for a duration of at least 1 second, Code 73 is set. Once code 73 is set, the force motor is disabled and full line pressure will be applied until the next time the ignition key is cycled. Code 73 will remain stored but the force motor will resume normal function until the conditions for code 73 re-occur.

Force motor circuit check. 1991 Models:

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This procedure verifies an amperage difference of .16 amp or more and tests the PCM/TCM's ability to control amperage to the force motor.

2. This part of the test checks the force motor for internal shorts and integrity.


Diagnostic Aids:
Check for poor connections at PCM/TCM and especially at transmission pass-thru connector.