P0785

Diagnostic Chart:

Wiring Diagram:

Circuit Description

The 3-2 Shift Solenoid Valve Assembly (3-2 SS Valve Assy) is a normally-closed, 3-port, on/off device. The device controls the 3-2 downshift. The solenoid attaches to the control valve body within the transmission. Circuit 439 supplies ignition voltage directly to the solenoid. The 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.

If the PCM detects a continuous open or short to ground in the 3-2 SS Valve Assy circuit or the 3-2 SS Valve Assy., then DTC P0785 sets. DTC P0785 is a type A DTC.

Conditions for Setting the DTC
- The System Voltage is 10-16 volts.
- The engine speed is greater than 400 RPM for 5 seconds and not in fuel cut off.
- The PCM commands the solenoid ON and the voltage remains high (Battery Positive Voltage).
- The PCM commands the solenoid OFF and the voltage remains low (0 volts).
- All conditions are met in 5 seconds.

Action Taken When the DTC Sets
- The PCM commands a soft landing to third gear.
- The PCM commands maximum line pressure.
- The PCM freezes shift adapts from being updated.
- The PCM inhibits the TCC engagement.
- The PCM inhibits 4th gear if in hot mode.
- The PCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC
- The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported
- A scan Tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
- The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

Diagnostic Aids

- Inspect the wiring for any poor electrical connections at the PCM. Inspect the wiring at the transmission 20-way connector. Look for the following problems:
- A bent terminal
- A backed out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation
- When diagnosing for an intermittent short or an open, massage the wiring harness while watching the test equipment for changes.

Test Description

The item numbers below refer to the step numbers on the diagnostic chart.
4. This step verifies that the PCM can control the 3-2 Shift solenoid Valve Assembly.
5. This step verifies that the 3-2 Shift Solenoid Valve Assembly receives power from the ignition through the fuse.
7. This step verifies that the PCM and the wiring properly control the ground circuit.
9. This step measures the resistance of the automatic transmission wiring harness. This step then compares the actual resistance to the expected resistance.