With 4L60-E Automatic Transmission

WITH 4L60-E AUTOMATIC TRANSMISSION

DTC 73 Flow Chart:

Transmission Pressure Control Solenoid Circuit:

(Figure 3) Line Pressure Chart:

CIRCUIT DESCRIPTION
The Pressure Control Solenoid (PCS) is a Powertrain Control Module (PCM) controlled device used to regulate transmission line pressure. The PCM compares Throttle Position (TP) voltage, engine RPM and other inputs to determine the line pressure appropriate for a given load.

The PCM will regulate the pressure by applying a varying amperage to the pressure control solenoid. The applied amperage can vary from 0.1 to 1.1 amp. The PCM then monitors the amperage at the return line.

DIAGNOSTIC TROUBLE CODE (DTC) 73 WILL SET WHEN
The return amperage varies greater than 0.16 amp from the commanded amperage, for at least one second, and no DTC 75 stored.

ACTION TAKEN (PCM WILL DEFAULT TO)
Full line pressure will be applied causing harsh shifts. DTC 73 will be stored in the PCM memory but will NOT turn "ON" the Malfunction Indicator Lamp (MIL).

DTC 73 WILL CLEAR WHEN
The fault condition(s) no longer exists, and the ignition switch is cycled "OFF" then "ON."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart:

1. This test checks the ability of the PCM to command the pressure control solenoid.
2. This test checks internal transmission harness and the pressure control solenoid for incorrect resistance.

DIAGNOSTIC AIDS
- Check for poor connections at PCM and at transmission connector.
- If pressure readings differ greatly from the line pressure chart, refer to the appropriate "Diagnostic Chart".