4L80E Automatic Transmission

DTC 73:

Pressure Control Solenoid Circuit:

CIRCUIT DESCRIPTION
The pressure control solenoid 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. The PCM/TCM will regulate the pressure by applying a varying current. The applied amperage can vary from 1 to 1.1 amp. The PCM/TCM then monitors the amperage at the return line and if the return amperage varies more than 0.16 amp from the commanded amperage for a duration of at least 1 second, Code 73 is set. Once Code 73 is set, the pressure control solenoid 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.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Checks the ability of the PCM/TCM to command the pressure control solenoid.

2. Checks for voltage at PCM/TCM.

3. Checks internal transmission harness and pressure control solenoid for low resistance.

4. Checks for short to ground.

5. Checks internal transmission harness and pressure control solenoid for high resistance.


DIAGNOSTIC AIDS
Check for poor connections at PCM/TCM and at transmission pass-thru connector.