TC20 - Key On Engine Off Service Code 621/622/641/643

Key On Engine Off Diagnostic Trouble Codes (DTC) 621 (SS1), 622 (SS2), 641 (SS3) and 643 (TCC) indicate a failure in the respective shift solenoid circuit.

Possible causes:
- Open harness.
- Shorted harness (ground or power).
- Damaged shift solenoid.
- Damaged Powertrain Control Module (PCM).

- Key "OFF".

- Disconnect transmission connector (12 pin at transmission).

- Measure resistance between suspect shift solenoid circuit at transmission connector and chassis ground.

- If the resistance between 13 and 27 ohms?

Yes -- Go to TC21. TC21 - Check Shift Solenoid Circuit For Short to Power

No -- Go to TC25. TC25 - Inspect Transmission Wiring