Oxygen Sensor: Testing and Inspection

CIRCUIT DIAGRAM

TROUBLESHOOTING HINTS
1. If the HO2S is defective, abnormally high emissions may occur.
2. If the HO2S check results were 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 volume air flow sensor, intake air temperature sensor, barometric pressure sensor, engine coolant temperature sensor.





Using GST











HARNESS INSPECTION PROCEDURES

INSPECTION

NOTE:
(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.











1. Disconnect the oxygen sensor connector, and measure the resistance between terminal 3 and terminal 4.





Standard value

2. Replace the oxygen sensor if there is malfunction.
3. Apply battery voltage directly between terminal 3 and terminal 4.

NOTE: Take care when applying the voltage. Damage will result if the terminals are incorrect or are short circuited.





4. Connect a digital-type voltmeter between terminal 1 and terminal 2.





5. While repeatedly racing the engine, measure the oxygen sensor output voltage.
6. If there is a problem, there may be an oxygen sensor malfunction.

Tightening torque
Heated oxygen sensor: 40 - 50 Nm
(400 - 500 kg.cm, 29 - 36 lb.ft)