P0785

Circuit Description

The 3 - 2 shift solenoid (SS) valve assembly 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 circuit 239. The powertrain control module (PCM) controls the solenoid by providing a ground path on circuit 687. 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 open or short to ground in the 3 - 2 SS valve assembly circuit or the 3 - 2 SS valve assembly, then DTC P0785 sets. DTC P0785 is a type A DTC.

Conditions for Running the DTC

^ The system voltage is 9-18 volts.
^ The engine speed is greater than 450 RPM for 5 seconds.
^ The engine is not in fuel cutoff.

Conditions for Setting the DTC

DTC P0785 sets if either of the following conditions occurs for 5 seconds:

^ The PCM commands the solenoid ON and the voltage input remains high (B+).
^ The PCM commands the solenoid OFF and the voltage input remains low (0 volts).

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 if the transmission is in hot mode.
^ The PCM freezes shift adapts from being updated.
^ The PCM stores DTC P0785 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 clears the DTC from PCM history.
^ 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 the ignition switch is OFF tong enough in order to power down the PCM.

Diagnostic Aids

^ Inspect the wiring at the PCM, the transmission connector and all other circuit connecting points for the following conditions:
- A backed out terminal
- A damaged terminal
- Reduced terminal tension
- A chafed wire
- A broken wire inside the insulation
- Moisture intrusion
- Corrosion
^ When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

Test Description

The 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 power to the 3 - 2 SS valve assembly.
7. This step tests the ability of the PCM and wiring to control the ground circuit.
9. This step measures the resistance of the automatic transmission (A/T) wiring harness assembly and the 3 - 2 SS valve assembly.