DTC P0785 3-2 Shift Solenoid Circuit Electrical

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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 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 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 10-19 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 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 TCC engagement.
The VCM inhibits 4th gear if the transmission is in hot mode.
The VCM freezes shift adapts from being updated.
The VCM stores DTC P0785 in VCM history.

Conditions for Clearing the MIL/DTC

The VCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
A scan tool clears the DTC from VCM history.
The VCM clears the DTC from VCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
The VCM cancels the DTC default actions when the fault no longer exists and the ignition switch 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 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 item numbers below refer to the step numbers on the diagnostic table.

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

This step tests for voltage to the solenoid.

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

This step measures the resistance of the automatic transmission (A/T) wiring harness assembly and the 3-2 SS valve assembly.

DTC P0785 3-2 SS Circuit Electrical

Step	Action	Value(s)	Yes	No
1	Was the Powertrain On-Board Diagnostic (OBD) System Check performed?	--	Go to Step 2	Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
2	Install the Scan Tool . With the engine OFF, turn the ignition switch to the RUN position. Important Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the VCM. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Are any of the following DTCs also set? P0740 P0753 P0758 P1860	--	Go to Step 3	Go to Step 4
3	Inspect the TRANS fuse. If the fuse is open, inspect the following components for a short to ground: Circuit 1020 (PNK) The solenoids The A/T wiring harness assembly Refer to General Electrical Diagnosis Procedures in Wiring Systems. Repair the circuit, the solenoids and the harness if necessary. Refer to Wiring Repairs in Wiring Systems. Did you find a short to ground condition?	--	Go to Step 16	Go to Step 5
4	Using the transmission output control function on the scan tool, command the 3-2 SS valve assembly ON and OFF three times, while listening to the bottom of the transmission pan (a stethoscope may be necessary). Did the solenoid click when commanded?	--	Go to Diagnostic Aids	Go to Step 5
5	Turn the ignition OFF. Disconnect the transmission 20-way connector (additional DTCs may set). Install the J 39775 jumper harness on the engine side of the 20-way connector. With the engine OFF, turn the ignition switch to the RUN position. Connect a test lamp from J 39775 jumper harness cavity E to ground. Refer to Automatic Transmission Inline Harness Connector End View . Does the test lamp illuminate?	--	Go to Step 7	Go to Step 6
6	Important The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Power Distribution Schematics in Wiring Systems for complete circuit distribution. Repair the open or short to ground in ignition feed circuit 1020 (PNK) to the 3-2 SS valve assembly. Refer to Wiring Repairs in Wiring Systems. Is the repair complete?	--	Go to Step 16	--
7	Install a test lamp between cavity E and cavity S of the J 39775 jumper harness. Using the transmission output control function on the scan tool, command the 3-2 SS valve assembly ON and OFF three times. Does the test lamp illuminate when you command the shift solenoid ON, and turn off when you command OFF?	--	Go to Step 10	Go to Step 8
8	Inspect circuit 687 (WHT) of the engine wiring harness for an open, short to ground or short to power condition. Refer to General Electrical Diagnosis Procedures in Wiring Systems. Repair the circuit if necessary. Refer to Wiring Repairs in Wiring Systems. Did you find an open, short to ground or short to power condition?	--	Go to Step 16	Go to Step 9
9	Replace the VCM. Refer to VCM Replacement/Programming in Engine Controls. Is the replacement complete?	--	Go to Step 16	--
10	Install the J 39775 jumper harness on the transmission side of the 20-way connector. Using the J 39200 DMM and the J 35616-A connector test adapter kit, measure the resistance between the terminal E and terminal S of the J 39775 jumper harness. Refer to Automatic Transmission Inline Harness Connector End View . Is the resistance within the specified range?	20-32 ohms	Go to Step 12	Go to Step 11
11	Disconnect the A/T wiring harness assembly from the 3-2 SS valve assembly. Measure the resistance of the 3-2 SS valve assembly. Is the resistance within the specified range?	20-32 ohms	Go to Step 14	Go to Step 15
12	Measure the resistance between terminal S and ground. Measure the resistance between terminal E and ground. Are both measurements greater than the specified value?	250 K ohms	Go to Diagnostic Aids	Go to Step 13
13	Disconnect the A/T wiring harness assembly from the 3-2 SS valve assembly. Measure the resistance between the component's terminals and ground. Are both readings greater than the specified value?	250 K ohms	Go to Step 14	Go to Step 15
14	Replace the A/T wiring harness assembly. Refer to TCC PWM Solenoid, TCC Solenoid, and Wiring Harness replacement. Is the replacement complete?	--	Go to Step 16	--
15	Replace the 3-2 SS valve assembly. Refer to Control and Shift Solenoids Replacement. Is the replacement complete?	--	Go to Step 16	--
16	Perform the following procedure in order to verify the repair: Select DTC. Select Clear Info. Drive the vehicle in D3 or D4 and perform a 3-2 downshift. Ensure that the following conditions are met: The VCM commands the 3-2 SS valve assembly ON, and the voltage input drops to zero. The VCM commands the 3-2 SS valve assembly OFF, and the voltage input increases to B+. All conditions are met for 5 seconds. Select Specific DTC. Enter DTC P0785. Has the test run and passed?	--	System OK	Go to Step 1