P0171/0172 1/1 Fuel System Lean/Rich

SYMPTOM LIST
P-0171 1/1 FUEL SYSTEM LEAN
P-0172 1/1 FUEL SYSTEM RICH

Test Note: All symptoms listed above are diagnosed using the same tests.


POSSIBLE CAUSES
- Coolant sensor calibration failure
- Engine mechanical problem
- Fuel pressure out of specification
- Upstream 02 sensor heater defect
- Fuel system rich or lean does not reoccur