51 Engine coolant temperature circuit open
How to read it
Code 51 reads as 5 flashes, pause, 1 flash on the check-engine light. Jumper the self-test input to signal return at the test connector, then run the key on engine off self test and the running self test, counting the check-engine flashes each time.
New to flash codes? The OBD-I code reading guide walks through the paperclip method, code 12, and reading two-digit codes.
What does Ford code 51 mean?
51. Engine coolant temperature circuit open. This code sets when your vehicle computer detects engine coolant temperature circuit open.
Common causes of 51
- Unplugged or failed coolant temperature sensor
- Open circuit in the sensor wiring
- Corroded or loose connector
- Open PCM input circuit
- Broken sensor
How to fix 51
- Confirm the code and check the sensor is plugged in
- Inspect the sensor connector and wiring for an open circuit
- Test the sensor resistance against the factory chart
- Repair wiring before replacing the sensor
- Replace the sensor only after the wiring test fails