Oxygen Sensor: Testing and Inspection

CIRCUIT DIAGRAM





INSPECTION USING SCAN TOOL





HARNESS INSPECTION PROCEDURE

SENSOR INSPECTION

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











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

Standard value: 30 Ohms or more at 400°C (752°F)

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.

Engine Racing: Minimum 0.6 Volts

NOTE: Makes the air/fuel mixture rich by increased engine speed.

6. If there is a problem, it is probable that there is a malfunction of the oxygen sensor.

Oxygen sensor torque: 40 - 50 Nm (29 - 36 ft lb)

TROUBLESHOOTING 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 specifications, 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.