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 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 10-19 volts. |
| • | The engine speed is greater than 450 RPM for 8 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 remains high (B+). |
| - | The VCM commands the solenoid OFF and the voltage remains low (0 volts). |
Action Taken When the DTC Sets
| • | The VCM commands a soft landing to third gear. |
| • | The VCM commands maximum line pressure. |
| • | The VCM freezes shift adapts from being updated. |
| • | The VCM inhibits TCC engagement. |
| • | The VCM inhibits 4th gear if the transmission is in hot mode. |
| • | The VCM illuminates the Malfunction Indicator Lamp (MIL). |
Conditions for Clearing the MIL/DTC
| • | The VCM turns OFF the MIL after three consecutive ignition cycles 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 for poor electrical connections at the VCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look 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 |
| • | 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 Wiring Harness Assembly and the 3-2 SS Valve Assy.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Were you sent here from the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to OBD System Check | |||||||
2 |
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Are DTCs P0740, P0753, P0758 and P1860 also set? | -- | ||||||||
3 |
Did you find and correct a problem? | -- | -- | |||||||
Command the 3-2 SS Valve Assy. ON and OFF three times, while listening to the bottom of the transmission pan (a stethoscope may be necessary). Does the solenoid click when commanded? | -- | Go to Diagnostic Aids | ||||||||
Does the test lamp illuminate? | -- | |||||||||
6 | Repair the open or short to ground in ignition feed circuit 1020 to the 3-2 SS Valve Assy. Refer to Electrical Diagnosis, Section 8A. Is the repair complete? | -- | -- | |||||||
Does the test lamp illuminate when you command the shift solenoid ON and turn OFF when you command OFF? | -- | |||||||||
8 | Inspect circuit 687 for an open or short to ground. Repair the circuit if necessary. Refer to Electrical Diagnosis, Section 8A. Did you find a problem? | -- | ||||||||
Is the resistance within the specified range? | 20-32 ohms | |||||||||
10 | Replace the VCM. Refer to VCM Replacement, Section 6. Is the replacement complete? | -- | -- | |||||||
11 |
Is the resistance within the specified range? | 20-32 ohms | ||||||||
12 |
Are both measurements greater than the specified value? | 250 K ohms | Go to Diagnostic Aids | |||||||
13 |
Are both readings greater than the specified value? | 250 K ohms | ||||||||
14 | Replace the Automatic Transmission Wiring Harness Assembly. Refer to 4L60-E Automatic Transmission On-Vehicle Service. Is the replacement complete? | -- | -- | |||||||
15 | Replace the 3-2 Shift Solenoid Valve Assembly. Refer to 3-2 Shift Solenoid Valve Assembly Replacement/4L60-E Automatic Transmission On-Vehicle Service. Is the replacement complete? | -- | -- | |||||||
16 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
