Possible Causes
Possible causes are:
Fuel System
- Contaminated fuel injector(s).
- Excessive fuel pressure.
- Leaking fuel injector(s).
- Leaking fuel pressure regulator.
- Low fuel pressure or running out of fuel.
Induction System
- Air leaks after MAF sensor.
- Improperly seated engine oil dipstick.
- PCV system.
- Vacuum leaks.
EGR System
- Leaking gasket.
- Stuck open EGR valve.
Base Engine
- Cam timing.
- Cylinder compression.
- Engine oil overfill.
- Exhaust leaks before or near HO2S.
- Leaking diaphragm.
Electrical
- Damaged HO2S.
- Damaged PCM.
- Open or shorted HO2S.
- Short to VPWR in harness or HO2S.
- Water in harness connector.