551 Intake air control circuit failure KOEO
How to read it
Code 551 reads as 5 flashes, pause, 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 551 mean?
551. Intake air control circuit failure KOEO. This code sets when your vehicle computer detects intake air control circuit failure koeo.
Common causes of 551
- Disconnected or leaking secondary air hose
- Faulty air pump, diverter or bypass valve
- Open or shorted wiring in the air control circuit
- Corroded connector at the air control solenoid
- Faulty PCM air control output
How to fix 551
- Confirm the code and read the flash sequence again
- Inspect the secondary air hoses for leaks and disconnects
- Test the air pump and control valves for operation
- Repair a hose or wiring fault before replacing parts
- Replace a failed valve or solenoid only after the tests