A/F (Air Fuel Ratio) Sensor On-Vehicle Inspection

A/F (Air Fuel Ratio) Sensor On-Vehicle Inspection

A/F Sensor
1. Check that A/F sensor signal is output properly.
If faulty condition is found, check the following.
- Wire harness and connections
- Exhaust system leakage
If check results are satisfactory, replace A/F sensor.

A/F Sensor Heater
1. Turn OFF ignition switch and disconnect A/F sensor connector.
2. Check that voltage of A/F sensor connector (vehicle side) between terminals "4" and "3" is battery voltage when ignition switch is in ON position.
If faulty condition is found, check power supply circuit, ground circuit and connections.







3. Using ohmmeter, measure resistance of A/F sensor connector (sensor side) between terminals "3" and "4" at A/F sensor connector. If faulty condition is found, replace A/F sensor.

NOTE: Sensor temperature affects resistance value largely. Make sure that sensor heater is at specified temperature.

A/F sensor heater resistance
2.16 - 2.64 ohms at 20 °C (68 °F)