Oxygen Sensor Preliminary Tests
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Check for the following conditions which can cause Oxygen Sensor Faults to set without requiring Oxygen Sensor replacement:
Common issues for lean faults:
- Vacuum leaks - check for failed or loose vacuum lines, leaking intake gaskets, or any other source of un - metered air leaks (leaks after the Mass Air Flow Sensor).
- Restricted fuel filter or bent/pinched fuel system lines.
- Incorrect input from other sensors, such as the Mass Air Flow Sensor, which may not always set a fault.
- Engine misfire.
- Exhaust leaks.
- Camshaft timing.
Common issues for rich faults:
- Leaking or faulty fuel injector.
- Fuel injector driver shorted in ECM, or wiring short for injectors (short to ground).
- Leaking or faulty fuel pressure regulator or restricted return line.
- Faulty fuel pump or fuel pump driver module.
- Incorrect input from other sensors, such as the Mass Air Flow Sensor, which may not always set a fault.
- Aftermarket components or performance chips.
- Camshaft timing.