Transmission Control Module (TCM) - 8HP45

P0657-ACTUATOR SUPPLY VOLTAGE "A" CIRCUIT/OPEN

For a complete wiring diagram Refer to the Wiring Information.

Theory of Operation

The purpose of the monitoring is to detect electrical circuit failures in the power supply of the solenoid and pressure regulator output stages. This monitoring is performed by comparing the output stage power supply voltage level to a predefined voltage range to detect an open circuit, short to ground or short to battery failures. In addition, the activation of the power supply of the output stages is checked to identify any failures that inhibit the activation of the power supply.

- When Monitored:
Battery voltage is in a valid range.

Calibrated amount of time expired after output stage power supply is switched from ON to OFF or from OFF to ON.

Power supply is switched OFF.

TCM in initialization.

- Set Condition:
An open circuit failure is detected if the power supply voltage is in a range witch indicates an open circuit.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. 8HP45 Pre-Diagnostic Troubleshooting Procedure

1. CHECK IF DTC IS CURRENT

NOTE: The Transmission Control Module stores under Environmental Data the transmission operating conditions when the DTC was set. Before erasing any DTCs, record all information pertaining to the DTC.

1. With the scan tool, erase transmission DTCs.
2. Using the Environmental Data previously recorded, drive the vehicle and try to duplicate the condition in which the DTC set.

Does the DTC reset?

Yes

- Go To 2

No

- Go To 3

2. TRANSMISSION CONTROL MODULE ASSEMBLY (TCMA)

If there are no possible causes remaining, view repair.

Repair

- Using the schematics as a guide, check the TCMA terminals for corrosion, damage or terminal push out. Pay particular attention to power and ground circuits. Check Service Information Tune-ups or Service Bulletins for possible causes that may apply. Remove the transmission oil pan and the TCMA. Valve Body - Removal. Inspect and clean the solenoid terminals at the wiring harness leadframe for metallic contamination. Reinstall the TCMA. Valve Body - Installation. Connect the scan tool and erase the DTCs. Road test the vehicle and check for DTCs. If the DTC returns, replace and program the TCMA. Valve Body - Removal.
- Perform the TRANSMISSION VERIFICATION TEST. Verification Tests.

3. INTERMITTENT WIRING AND CONNECTORS
1. The conditions necessary to set this DTC are not present at this time.
2. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
3. Wiggle the wiring and connectors while checking for any possible open or shorted circuits.
4. Check for any Service Information Tune-ups or Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the TRANSMISSION VERIFICATION TEST. Verification Tests.

No

- Test Complete.