P0788
DTC P0788 (4.2L)
Circuit Description
The 3-2 shift solenoid (SS) valve is a normally-closed, 3-port, ON/OFF device that controls the 3-2 downshift. The solenoid attaches to the control valve body within the transmission. The solenoid receives voltage through the ignition voltage circuit. The powertrain control module (PCM) controls the solenoid by providing a ground path on the 3-2 shift solenoid valve control circuit. During a 3-2 downshift, the 2-4 band applies as the 3-4 clutch releases. The PCM varies the timing between the 3-4 clutch release and the 2-4 band apply depending on the vehicle speed and throttle position.
When the PCM detects a continuous short to voltage in the 3-2 shift solenoid valve control circuit, then DTC P0788 sets. DTC P0788 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0788 3-2 Shift Solenoid (SS) Control Circuit High Voltage
Conditions for Running the DTC
- The system voltage is 8-18 volts.
- The engine speed is 475 RPM for 5 seconds.
- Vehicle speed.
Conditions for Setting the DTC
DTC P0788 sets if the PCM commands the solenoid ON and the voltage feedback remains high, B+.
Action Taken When the DTC Sets
- The powertrain control module (PCM) requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL).
- The PCM commands third gear.
- The PCM commands maximum line pressure.
- The PCM freezes transmission adaptive functions.
- At the time of the first failure, the PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as a Failure Record.
- At the time of the second failure, the ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame.
- The PCM stores DTC P0788 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.
Conditions for Clearing the DTC
- The engine control module (ECM) turns OFF the MIL after the third consecutive drive trip in which the PCM does not send a MIL illumination request.
- 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 default actions when the ignition is OFF long enough in order to power down the PCM.
