Oxygen Sensor Diagnosis

A properly operating oxygen sensor may have unusual signal characteristics that are the result of other components. A malfunction of any of the following components may affect sensor signal characteristics:

^ Fuel injector(s)

^ Air flow sensor

^ Evaporative emission system

^ Intake air temperature sensor

^ Barometric pressure sensor

^ Engine coolant temperature sensor

^ Throttle position sensor

^ Intake system (vacuum) leaks

^ Low battery charge

^ Spark plugs

The PCM does not monitor either oxygen sensor signal when the engine management system is in open loop or when the purge solenoid is operating.

If codes other than oxygen sensor codes are present, diagnose/repair these conditions BEFORE continuing with oxygen sensor diagnosis.*

Note:
* A malfunctioning front oxygen sensor may cause fuel trim codes to set.

The scan tool and HDS testing procedures are provided in the following section. The scan tool test is a quick procedure that provides basic sensor information. The HDS testing procedure requires a more involved set up but provides more detailed information about the sensors performance.