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 that controls the 3-2 downshift. The solenoid attaches to the control valve body within the transmission. The solenoid receives ignition voltage through circuit 1020. The Vehicle Control Module (VCM) 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 VCM 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 VCM 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 450 RPM for 5 seconds.

^ Not in fuel cutoff.

^ All of the above conditions are met for 5 seconds, and either of the following fail conditions occurs for 5 seconds:

- The VCM commands the solenoid ON and the voltage input remains high (B+).

- The VCM commands the solenoid OFF and the voltage input remains low (0 volts).

ACTION TAKEN WHEN THE DTC SETS

^ The VCM illuminates the Malfunction Indicator Lamp (MIL).

^ The VCM commands a soft landing to third gear.

^ The VCM commands maximum line pressure.

^ The VCM inhibits Torque Converter Clutch (TCC) engagement.

^ The VCM inhibits 4th gear if the transmission is in hot mode.

^ The VCM freezes shift adapts from being updated.

^ DTC P0785 stores in VCM history.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The VCM turns OFF the MIL after three consecutive trips without a failure reported.

^ A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.

^ The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

DIAGNOSTIC AIDS

^ Inspect the wiring at the VCM, the transmission connector and all other circuit connecting point5 for the following conditions:

- A bent terminal.

- A backed out terminal.

- A damaged terminal.

- Poor 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 item numbers below refer to the step numbers on the diagnostic table.

4. This step tests the ability of the VCM to control the solenoid.

5. This step tests for voltage to the solenoid.

7. This step tests the ability of the VCM and the wiring to control the ground circuit.

10. This step measures the resistance of the Automatic Transmission Wiring Harness Assembly (A/T Wiring Harness Assembly), and the 3-2 SS Valve Assy.