The pressure control (PC) solenoid valve regulates actuator feed fluid passing through the solenoid into torque signal pressure. The transmission control module (TCM) uses a pulse width modulated signal in order to control the torque signal pressure. The TCM compares various inputs in order to determine the appropriate pressure for a given load. The TCM varies the current to the PC solenoid from 0.1 amps, for maximum line pressure to 1.1 amps, for minimum line pressure. An internal current monitor within the TCM provides feedback in order to determine actual PC solenoid valve current draw.

The ignition is ON.

The PC solenoid valve feedback circuit indicates a continuous open or short to ground for 1.2 seconds or greater.

DTC P0748 is a Type C DTC.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Transmission General Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Transmission Control Module Scan Tool Information

Special Tools

Using the scan tool, command several values of solenoid reference current from 0.1-1.1 amps and observe the PC Sol. Actual Current and the PC Sol. Ref. Current. The PC Sol. Actual Current should not vary from the PC Sol. Ref. Current by greater than 0.16 amp.

1. Disconnect the automatic transmission inline 20-way connector. Install the J 45681 jumper harness, on the transmission side on the connector. Using the J 35616 GM-approved terminal test kit, measure the resistance between the PC Solenoid high control circuit and the PC Solenoid low control circuit.

⇒	If the resistance is within 3.5-5.5 ohms, measure the resistance from the PC Sol. Valve high control circuit to ground.

⇒	If the resistance is greater than 5.5 ohms, test the high and low control circuit of the PC Solenoid for an open.

2. Measure the resistance between the PC solenoid high control circuit and the transmission case. Measure the resistance between the PC solenoid low control circuit and the transmission case. The resistance should be greater than 50K ohms.

⇒	If the resistance is less than 50K ohms, replace the automatic transmission wiring harness assembly.

3. Measure the resistance between the PC solenoid high control circuit and all other circuits of the J 45681 , except the PC solenoid low control circuit. Measure the resistance between the PC solenoid low control circuit and all other circuits of the J 45681 , except the PC solenoid high control circuit. The resistance should be greater than 10 ohms.

⇒	If the resistance is less than 10 ohms, replace the automatic transmission wiring harness assembly.

4. Remove the J 45681 from the transmission side and install the J 45681 on the engine side of the harness. Disconnect the TCM connector. Using the J 35616 , measure the resistance of the PC solenoid high control circuit between the TCM connector and the automatic transmission inline 20-way connector. Measure the resistance of the PC solenoid low control circuit between the TCM connector and the automatic transmission inline 20-way connector. The resistance should be less than 10 ohms for each circuit.

⇒	If the value is greater than 10 ohms repair the open in the affected circuit.

5. Measure the resistance between the PC solenoid high control circuit and ground. Measure the resistance between the PC solenoid low control circuit and ground. The resistance for each circuit should be greater than 10 ohms.

⇒	If the value is less than 10 ohms repair the short to ground in the affected circuit.

6. Connect the TCM connector. Turn ON the ignition, with the engine OFF. Test the PC solenoid high control circuit and the PC solenoid low control circuit for a short to voltage.

⇒	If a short to voltage condition is found, repair as necessary.

7. If all circuits/connections test normal, test or replace the PC solenoid valve.

Verify the PC solenoid valve resistance is between 3.5-5.5 ohms.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.