Possible Causes
- The engine control module measures a signal that remains low when transitions are expected
- Air leakage between heated oxygen sensor and catalyst
- Heated oxygen sensor circuit, short circuit to ground, short circuit to power, open circuit, high resistance
- Air leakage between catalyst and exhaust manifold flange
- Heated oxygen sensor tip contaminated by excessive oil consumption
- Heated oxygen sensor tip contaminated by poor or incorrect fuel
- Heated oxygen sensor failure