P0748

DTC P0748





Circuit Description
The transmission control module (TCM) 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 TCM compares TP voltage, fluid temperature, gear states, and other inputs in order to determine the line pressure appropriate for a given load. The TCM 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 TCM then monitors the amperage at the return line.
When the TCM detects a continuous open, short to ground or short to voltage in the PC solenoid valve circuit, DTC P0748 sets. DTC P0748 is a type C DTC.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0748 Pressure Control (PC) Solenoid Control Circuit

Conditions for Running the DTC
The engine is running.

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 TCM does not request the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL).
^ The TCM requests the ECM to illuminate the service vehicle soon (SVS) lamp.
^ The TCM commands maximum line pressure.
^ The TCM freezes transmission adaptive functions.
^ The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
^ The TCM stores DTC P0748 in TCM history.

Conditions for Clearing the SVS Lamp/DTC
^ The TCM clears the SVS lamp request when the condition no longer exists.
^ A scan tool can clear the SVS Lamp/DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
^ The TCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the TCM.

Test Description











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