P0171

Test 1:

Tests 2 - 5:

Test 6:

SYMPTOM
P0171 1/1 FUEL SYSTEM LEAN P 0172 ill FUEL SYSTEM RICH

WHEN MONITORED
With the engine running in closed loop mode and the ambient/battery temperature above 20 °F and altitude < 8000 ft.

SET CONDITION
PCM conducts test to determine whether fuel system is running too lean. If this happens for 2 trips, MIL illuminates and a trouble code is stored. MIL remains ON for more than 1 trip but goes out if conditions that set code are not found on subsequent trips

POSSIBLE CAUSES
- Coolant sensor calibration
- Engine mechanical problem
- Fuel pressure out of specification
- Upstream O2 sensor heater
- Fuel system rich or lean intermittent defect