41 Fuel system indicates lean or oxygen sensor not switching
How to read it
Code 41 reads as 4 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 41 mean?
41. Fuel system indicates lean or oxygen sensor not switching. This code sets when your vehicle computer detects fuel system indicates lean or oxygen sensor not switching.
Common causes of 41
- Intake leak
- Fuel pressure low
- Fuel filter/pump
- Injectors
- HO2S
- AIR system
- MAF/MAP sensor
- ECM
How to fix 41
- Check for an intake leak
- Measure fuel pressure and compare it with the spec: this fault reads low
- Check the fuel filter and the fuel pump delivery
- Check the injectors for a clogged or a leaking one
- Test the HO2S and replace it only if it fails its own test
- Check the AIR system for a stuck valve, a blocked passage or a dead pump
- Test the MAF/MAP sensor and replace it only if it fails its own test
- Test the ECM last, only after every circuit test has passed
- Clear the code, then retest to confirm the fix holds