Heated Oxygen Sensor Check
HEATED OXYGEN SENSOR CHECKRequired Special Tools:
- MD998464: Test Harness
- MB991316: Test Harness
[Heated oxygen sensor (rear)]
1. Disconnect the heated oxygen sensor connector and connect special tool MD998464 to the connector on the heated oxygen sensor side.
2. Measure the resistance between terminal No. 1 (red clip) and terminal No. 3 (blue clip) on the heated oxygen sensor connector.
Standard value: 11 - 18 ohms [at 20 °C (68 °F)]
3. If there is no continuity, replace the heated oxygen sensor.
4. Warm up the engine until engine coolant is 80 °C (176 °F) or higher.
5. Drive at 50 km/h (31mph) or more for 10 minutes.
6. Connect a digital voltage meter between terminal No. 2 (black clip) and terminal No. 4 (white clip).
7. Measure the output voltage of the heated oxygen sensor under the following driving.
- Transaxle: 2nd speed
- Drive with wide open throttle
- Engine: 3,500 r/min or more
NOTE: If the temperature of sensing area does not reach the high temperature [of approximately 400 °C (752 °F) or more] even though the oxygen sensor is normal, the output voltage would be possibly low in spite of the rich air-fuel ratio.
8. If the output voltage is not within the standard value, replace the heated oxygen sensor.
[Heated oxygen sensor (front)]
1. Disconnect the heated oxygen sensor connector and connect special tool MB991316 to the connector on the heated oxygen sensor side.
2. Measure the resistance between terminal No. 1 (red clip) and terminal No. 3 (blue clip) on the heated oxygen sensor connector.
Standard value: 4.5 - 8.0 ohms [at 20 °C (68 °F)]
3. If there is no continuity, replace the heated oxygen sensor.
4. Warm up the engine until engine coolant is 80 °C (176 °F) or higher.
5. Rev the engine for 5 minutes or more with the engine speed of 2,000 r/min.
6. Connect a digital voltage meter between terminal No. 2 (black clip) and terminal No. 4 (white clip).
7. While repeatedly revving the engine, measure the heated oxygen sensor output voltage.
CAUTION:
- Be very careful when connecting the jumper wire; incorrect connection can damage the heated oxygen sensor.
- Be careful the heater is broken when voltage of beyond 8 volts is applied to the heated oxygen sensor heater.
NOTE: If the temperature of sensing area does not reach the high temperature [of approximately 400 °C (752 °F) or more] even though the oxygen sensor is normal, the output voltage would be possibly low in spite of the rich air-fuel ratio. Therefore, if the output voltage is low, use jumper wires to connect the terminal No. 1 (red clip) and the terminal No. 3 (blue clip) of the heated oxygen sensor with a (+) terminal and (-) terminal of 8 volts power supply respectively, then check again.
8. If the output voltage is not within the standard value, replace the heated oxygen sensor.