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 339. 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 8-18 volts. |
| • | The engine speed is greater than 300 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 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 the 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 long 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.
-
This step tests the ability of the PCM to control the solenoid.
-
This step tests for power to the 3-2 SS valve assembly.
-
This step tests the ability of the PCM and wiring to control the ground circuit.
-
This step measures resistance of the automatic transmission (A/T) wiring harness assembly and the 3-2 SS valve assembly.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||
2 |
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 PCM. Are any of the following DTCs also set?
| -- | ||||||||||
3 |
Refer to Wiring Repairs in Wiring Systems. Was a short to ground condition found? | -- | ||||||||||
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 | ||||||||||
Is the test lamp ON? | -- | |||||||||||
6 |
Important: The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Electrical Diagnosis for complete circuit distribution. Repair the open or short to ground in ignition feed circuit 339 (PNK) to the 3-2 SS valve assembly. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||||
Is the test lamp ON when the solenoid is commanded ON, and OFF when the solenoid is commanded OFF? | -- | |||||||||||
8 |
Refer to General Electrical Diagnosis in Wiring Systems. Refer to Wiring Repairs in Wiring Systems. Was an open, short to ground or short to power condition found? | -- | ||||||||||
9 | Replace the PCM. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement in Engine Controls. Is the replacement complete? | -- | -- | |||||||||
Is the resistance within the specified range? | 20-32 ohms | |||||||||||
11 |
Is the resistance within the specified range? | 20-32 ohms | ||||||||||
12 | Measure the resistance between terminal S and ground, and between terminal E and ground. Are both measurements greater than the specified value? | 250 K ohms | Go to Diagnostic Aids | |||||||||
13 |
Are both measurements greater than the specified value? | 250 K ohms | ||||||||||
14 | Replace the A/T wiring harness assembly. Refer to Torque Converter Clutch Pulse Width Modulation Solenoid, Torque Converter Clutch Solenoid, and Wiring Harness Replacement. Is the replacement complete? | -- | -- | |||||||||
15 | Replace the 3-2 SS valve assembly. Refer to Control and Shift Solenoids Replacement . Is the replacement complete? | -- | -- | |||||||||
16 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | System OK |
