P0748

CIRCUIT DESCRIPTION

The Pressure Control Solenoid Valve (PC Sol. Valve) regulates actuator feed fluid passing through the solenoid into torque signal pressure. The Powertrain Control Module (PCM) uses a pulse width modulated signal in order to control the torque signal pressure. The PCM compares various inputs in order to determine the appropriate pressure for a given load. The PCM varies the current to the PC Sol. Valve from 0.1-1.1 amp. An internal current monitor within the PCM provides feedback in order to determine actual PC Sol. Valve current draw.

If the PCM detects a commanded current draw that differs from the actual current draw by more than a calibrated value, then DTC P0748 sets. DTC P0748 is a Type C DTC.

CONDITIONS FOR SETTING THE DTC

^ No Incorrect Gear Ratio DTC P0730 is set.
^ No Maximum Adapt. and Long Shift DTC P1811 is set.
^ The system voltage is 10-17 volts.
^ The engine has been running for more than 1 second.
^ The difference between the commanded PC Sol. Valve current and the actual PC Sol. Valve current is 0.05 amps or more.

ACTION TAKEN WHEN THE DTC SETS

^ SERVICE VEHICLE SOON, SERVICE TRANSMISSION displays on the Driver Information Center (DIC).
^ The PCM commands maximum line pressure.
^ The PCM disables steady state adapts.
^ The PCM disables upshift adapts.
^ The PCM disables garage shift adapts.
^ The PCM inhibits torque management.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The commanded PC Sol. Valve current and the actual PC Sol. Valve current are within 0.05 amps of each other for 2 seconds.
^ 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.

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. Inspect the wiring for poor electrical connections at the PC Sol. Valve connector. Look for the following problems:

- 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, massage the wiring harness while watching the test equipment for a change.

TEST DESCRIPTION

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

2. This step verifies that the PCM responds to scan tool commands, and that the DTC could set intermittently.
3. This step verifies that the resistance value is within specifications. Use the J 35616 Test Connector Adapter Kit, in order to avoid damaging the terminals.