P0748

Circuit Description with 4T80-E Automatic Transaxle

Pressure Control Solenoid Schematic:

The Pressure Control (PC) solenoid valve regulates actuator feed fluid passing through the solenoid into torque signal pressure. The 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 solenoid valve from 0.1 amps, for maximum line pressure to 1.1 amps, for minimum line pressure. An internal current monitor within the PCM provides feedback in order to determine actual PC solenoid valve current draw.

If the PCM detects a continuous open, short to ground or short to voltage in the PC solenoid valve circuit, then DTC P0748 sets. DTC P0748 is a type C DTC.

CONDITIONS FOR RUNNING THE DTC
^ The system voltage is 10.7 volts or greater.
^ The engine run time is greater than 1 second.

CONDITIONS FOR SETTING THE DTC
The PC solenoid valve feedback circuit indicates a continuous open, short to ground or short to voltage for greater than 0.1 second

ACTION TAKEN WHEN THE DTC SETS
^ The PCM does not illuminate the Malfunction Indicator Lamp (MIL).
^ SERVICE TRANSMISSION displays on the driver information center (DTC).
^ The PCM commands maximum line pressure.
^ 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/DTC
^ The PCM clears the DTC when the condition no longer exists.
^ 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 fault no longer exists and/or the ignition switch is OFF long enough in order to power down the PCM.

DIAGNOSTIC AIDS
^ Inspect the connectors at the PCM, the PC solenoid valve, and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Diagrams.

TEST DESCRIPTION

Steps 1 - 6:

Steps 7 - 14:

Steps 15 - 20:

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.