P0788
DTC P0788
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 ignition voltage through the ignition 1 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 the throttle position.
When the PCM detects a continuous short to voltage in the 3-2 SS valve 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 engine speed is greater than 450 RPM for 5 seconds.
* The engine is not in fuel cutoff.
Conditions for Setting the DTC
DTC P0788 sets if the following condition occurs for 5 seconds:
The PCM commands the solenoid ON and the voltage feedback remains high, B+.
Action Taken When the DTC Sets
* The PCM illuminates the malfunction indicator lamp (MIL).
* The PCM commands a soft landing to third gear.
* The PCM commands maximum line pressure.
* The PCM inhibits torque converter clutch (TCC) engagement.
* The PCM inhibits fourth gear in Hot Mode.
* The PCM freezes transmission adaptive functions from being updated.
* The PCM inhibits 3-2 downshifts above 48 km/h (30 mph).
* The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
* The PCM stores DTC P0788 in PCM history.
Conditions for Clearing the MIL/DTC
* The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
* A scan tool can clear the MIL/DTC.
* The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an 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.
Test Description
The item numbers below refer to the step numbers on the diagnostic table.
4. This step tests the ability of the PCM to control the solenoid.
5. This step tests for voltage to the solenoid.
6. This step tests the ability of the PCM and the wiring to control the ground circuit.
8. This step measures the resistance of the automatic transmission wiring harness assembly and the 3-2 SS valve.
