P0748

DTC P0748

Schematic:

Circuit Description
The PCM uses the Pressure Control (PC) solenoid valve in order to regulate the transmission line pressure. The PC solenoid valve consists of an electrical connector, a coil, an armature, a regulating spring, and a poppet valve. The PC solenoid valve is attached to the control valve body. The PCM compares TP voltage, fluid temperature, gear states, and other inputs in order to determine the line pressure appropriate for a given load. The PCM regulates the pressure by applying a varying amperage to the PC solenoid valve. The applied amperage varies from 0.1 amps for maximum line pressure to 1.1 amps for minimum line pressure. The PCM then monitors the amperage at the return line.
When the PCM detects a continuous open, short to ground or short to voltage in the PC solenoid valve circuit, then DTC P0748 sets. DTC P0748is a type C DTC.

Conditions for Running the DTC
The system voltage is 8 - 18 volts.

Conditions for Setting the DTC
The PC solenoid valve duty cycle is 0 percent, or greater than 95 percent.

Action Taken When the DTC Sets
- The PCM does not illuminate the Malfunction Indicator Lamp (MIL).
- The PCM commands maximum line pressure, 0 amps.
- The PCM freezes transmission adapt functions.
- The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
- The PCM stores DTC P0748 in PCM history.

Conditions for Clearing the DTC
- A scan tool can clear the DTC.
- The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
- The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

Test Description

Steps 1-6:

Steps 7-14:

Steps 15-21:

The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies the ability of the PCM to command the PC solenoid valve.
3. This step verifies that the automatic transmission wiring harness and the PC solenoid valve have correct resistance.