Oxygen Sensor: Testing and Inspection

Circuit Diagram





Troubleshooting Procedures

Troubleshooting Hints
1. If the heated oxygen sensor is defective abnormally high emissions occur.
2. If the heated oxygen sensor check has resulted normal but the sensor output voltage is out of specification, check for the following items related to air fuel ratio control system.
- Faulty injector
- Air leaks in the intake manifold.
- Faulty mass air flow sensor, engine coolant temperature sensor.





Using Voltmeter











Harness Inspection Procedure

Sensor Inspection Procedure

NOTE: Before checking, warm up the engine until the engine coolant temperature reaches 80 to 95° C (176 to 205° F). Use an accurate digital voltmeter.

1. Disconnect the heated oxygen sensor connector, and measure the resistance between terminal 1 and terminal 2.

At temperature 400° C (752° F),
Resistance: 30 ohms or more

2. Replace the oxygen sensor if there is a malfunction.