P0748

Diagnostic Chart:

Diagnostic Chart (cont'd):

Wiring Diagram:

Circuit Description
The Pressure Control (PC) Sol. Valve is a PCM-controlled device that regulates the transmission line pressure. The PCM compares Accelerator Pedal Position (APP) Sensor voltage, engine RPM, and other inputs in order to determine the appropriate line pressure for a given load. The PCM regulates the pressure by applying a varying amperage to the PC Sol. Valve. The applied amperage varies from 0.1-1.1 amps. The PCM monitors the applied amperage. When the PCM detects a continuous open or short to ground in the PC Sol. Valve circuit or the PC Sol. Valve, then DTC P0748 sets. DTC P0748 is a type D DTC.

Conditions for Setting the DTC

^ The engine must be running for at least 5 seconds.
^ The difference in the commanded and the measured return amperage is greater than 0.16 amps.
^ All conditions met for 200 milliseconds (0.2 seconds).

Action Taken When the DTC Sets

^ The PCM disables the PC Sol. Valve, defaulting the transmission to maximum line pressure.
^ The PCM freezes shift adapts.
^ The PCM does not illuminate the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the DTC

^ A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

Diagnostic Aids

^ Inspect the wiring for poor electrical connections at the PCM Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following conditions:

- A bent terminal
- A backed out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation

^ When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.
^ First diagnose and clear any engine DTCs or APP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset.

Test Description
The numbers below refer to the step numbers on the diagnostic table.

2. This step tests the ability of the PCM to command the PC Sol. Valve.
3. This step tests the PC Sol. Valve and the internal wiring harness for incorrect resistance.