Oxygen Sensor: Testing and Inspection

CIRCUIT DIAGRAM





TROUBLESHOOTING PROCEDURES





USING VOLTMETER/SCAN TOOL
NOTE: If you release the accelerator pedal suddenly during engine running with about 4000 rpm, fuel supply will be stopped for awhile and the O2 sensor service data in the scan tool will be displayed in the range A. And when you suddenly press down the accelerator pedal will, the voltage will reache B range. 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 a good one.











HARNESS INSPECTION PROCEDURE

SENSOR INSPECTION

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 2 and terminal 3.





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

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

TROUBLE SHOOTING HINTS
1. If the heated oxygen sensor is defective abnormally high emissions may 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, EVAP valve and engine coolant temperature sensor.
- Wiring connection problem.