Oxygen Sensor: Testing and Inspection

CIRCUIT DIAGRAM










HARNESS INSPECTION PROCEDURE

SENSOR INSPECTION

NOTES:
(1) Before checking, warm up the engine until the engine coolant temperature reaches 80 to 95° C (176 to 205° F).
(2) Use an accurate digital voltmeter.
- Replace the oxygen sensor if there is a malfunction.
1 Disconnect the heated oxygen sensor connector, and measure the resistance between terminal 3 and terminal 4.




Standard Value

2. Replace the oxygen sensor if there is a malfunction

Heated oxygen sensor torque: 50-60 Nm (37-44 ft.lbs.)













TROUBLESHOOTING PROCEDURES

HINT: When the lean/rich period is above 2.6seconds in the condition that fully warm-up engine is 2,000 - 3,000 r.p.m and engine is above middle load.

HINTS:
1. If the heated oxygen sensor is defective abnormally, high emissions may occur.
2. If the heated oxygen sensor check has been normal, but the sensor output voltage is out of specification, check the following items related to the air fuel ratio control system.
- Faulty injector.
- Air leaks in the intake manifold.
- Faulty mass air flow sensor, EVAP valve and engine coolant temperature sensor.
- Wiring connection problem.
3. When O2 sensor output voltage is maintained as following for above 50 sec.
- Upstream: 0.4V - 0.6V
- Downstream : 0.4V - 0.5V




USING VOLTMETER

NOTE: If you release the accelerator pedal suddenly with the engine running about 4000 rpm, the fuel supply will be stopped for a while. When you suddenly press the accelerator pedal, the voltage will reach 'B' range. Then, when you let the engine idle again, the voltage fluctuates between 'A' and 'B' range. In this case, the O2 sensor can be determined as good.