P0657-SOLENOID SUPPLY VOLTAGE CIRCUIT
For a complete wiring diagram Refer to Section 8W
Theory of Operation
The Solenoid Supply Voltage output of the Transmission Control Module (TCM) provides the voltage to the three shift, two pressure and TCC solenoids. The output is active whenever the system is in normal operation. If a major system fault is detected, this output is turned off to ensure that no solenoids are active.
- When Monitored:
When the output is active and no undervoltage condition exists.
- Set Condition:
When the monitored supply voltage and battery voltage differ by 3.6 volts.
| Possible Causes |
| (T78) SOLENOID SUPPLY VOLTAGE CIRCUIT OPEN |
| (T78) SOLENOID SUPPLY VOLTAGE CIRCUIT SHORT TO GROUND |
| (T78) SOLENOID SUPPLY VOLTAGE CIRCUIT SHORT TO VOLTAGE |
| (T78) SOLENOID SUPPLY VOLTAGE CIRCUIT SHORT TO ANOTHER CIRCUIT |
| TRANSMISSION CONTROL MODULE |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
Diagnostic Test
1. (T78) SOLENOID SUPPLY VOLTAGE CIRCUIT SHORT TO VOLTAGEWith the scan tool, check for other transmission DTCs.
Is the DTC P1629-TCM INTERNAL - SOLENOID SUPPLY/WATCHDOG also present?
Yes
- When both P0657-SOLENOID SUPPLY VOLTAGE CIRCUIT and P1629-TCM INTERNAL - SOLENOID SUPPLY/WATCHDOG DTCs set at the same time indicates that the (T78) Solenoid Supply Voltage circuit is shorted to voltage. Repair the Solenoid Supply Voltage circuit for a short to voltage. If no short to voltage is present, using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found replace the TCM per the Service Information. Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES/TRANSMISSION CONTROL MODULE for the appropriate service procedures.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
- Go To 2
2. (T78) SOLENOID SUPPLY VOLTAGE CIRCUIT OPEN
Turn the ignition off to the lock position.
Disconnect the TCM C1 and C2 harness connectors.
Disconnect the Electrohydraulic Control Unit Assembly harness connector.
Measure the resistance of the (T78) Solenoid Supply Voltage circuit between the TCM C2 harness connector and the Electrohydraulic Control Unit Assembly harness connector.
Is the resistance above 5.0 ohms?
Yes
- Repair the (T78) Solenoid Supply Voltage circuit for an open.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
- Go To 3
3. (T78) SOLENOID SUPPLY VOLTAGE CIRCUIT SHORT TO GROUND
Measure the resistance between ground and the (T78) Solenoid Supply Voltage circuit.
Is the resistance below 5.0 ohms?
Yes
- Repair the (T78) Solenoid Supply Voltage circuit for a short to ground.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
- Go To 4
4. (T78) SOLENOID SUPPLY VOLTAGE CIRCUIT SHORT TO ANOTHER CIRCUIT
Measure the resistance between the (T78) Solenoid Supply Voltage circuit and all other circuits in the Electrohydraulic Control Unit Assembly harness connector.
Is the resistance below 5.0 ohms between the (T78) Solenoid Supply Voltage circuit and any other circuit(s) in the Electrohydraulic Control Unit Assembly harness connector?
Yes
- Repair the (T78) Solenoid Supply Voltage circuit for a short to another circuit(s).
- Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
- Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM per the Service Information. Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES/TRANSMISSION CONTROL MODULE for the appropriate service procedures.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)