P0748

Diagnostic Chart:

Diagnostic Chart (cont'd):

Wiring Diagram:

CIRCUIT DESCRIPTION

The Pressure Control Solenoid (PC Sol.) Valve is a PCM-controlled device that regulates the transmission line pressure. The PCM compares the Throttle Position (TP) voltage, the 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. The applied amperage varies from 0.1 to 1.1 amps. The PCM monitors the applied amperage.

When the PCM detects a continuous open or a continuous short to ground in the POS circuit, then DTC P0748 sets. DTC P0748 is a type D DTC.


CONDITIONS FOR SETTING THE DTC

- The system voltage is 10-17 volts.

- The PCM recognizes that the Pressure Control Solenoid Valve has reached the valve's electrical high limit.

- The PCM recognizes that the Pressure Control Solenoid Valve has reached the valve's electrical low limit.


ACTION TAKEN WHEN THE DTC SETS

- The PCM freezes shift adapts from being updated.

- 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 any poor electrical connections at the PCM. Inspect the wiring 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

- broken wire inside the insulation

- When diagnosing for an intermittent short or an open condition, massage the wiring harness while watching the test equipment for any changes.

TEST DESCRIPTION

The numbers below refer to the step numbers on the diagnostic chart.

2. This Step verifies that the PCM can command the PC Sol. Valve.

3. This Step verifies that the PC Sot. Valve has the correct resistance. This Step verifies that the Automatic Transmission wiring harness has the correct resistance.