171 Fuel system at adaptive limits

How to read it

Code 171 reads as 1 flash, pause, 7 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.

What does Ford code 171 mean?

171. Fuel system at adaptive limits. This code sets when your vehicle computer detects fuel system at adaptive limits.

Common causes of 171

• Intake leak/blocked
• Breather system
• Fuel pressure
• Fuel filter/pump
• Injectors
• HO2S
• AIR system
• EVAP system
• MAP sensor
• Ignition system
• ECM

How to fix 171

1. Check for an intake leak or a blockage
2. Check the breather system for a blockage
3. Check for fuel pressure
4. Check the fuel filter and the fuel pump delivery
5. Check the injectors for a clogged or a leaking one
6. Test the HO2S and replace it only if it fails its own test
7. Check the AIR system for a stuck valve, a blocked passage or a dead pump
8. Check the EVAP system for a leak or a stuck valve
9. Test the MAP sensor and replace it only if it fails its own test
10. Check for ignition system
11. Test the ECM last, only after every circuit test has passed
12. Clear the code, then retest to confirm the fix holds