Air Fuel Ratio (A/F) Sensor

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

WARNING: To avoid danger of being burned, do not touch exhaust system when system is hot. Sensor inspection should be performed when system is cool.

Heater
1. Disconnect A/F sensor connector.




2. Using ohmmeter, measure resistance of Sensor heater between terminals "VB" and "GND" at sensor connector. If found faulty, replace A/F sensor.

NOTE: Temperature of sensor affects resistance value largely. Make sure that sensor heater is at correct temperature.

A/F sensor heater resistance
2 - 3 Ohms at 20 degrees C (68 degrees F)

3. Connect A/F sensor connector securely.

Circuit Insulation Check
1. Disconnect connector from A/F sensor.

2. Using ohmmeter, check circuit insulation of A/F sensor. If faulty is found, replace A/F sensor.




- Between each heater terminal (1) and other than heater terminals (2).




- Between each terminal ((1), (2), (3) and (4)) of A/F sensor and A/F sensor body (5).

3. Connect A/F sensor connector securely.

Adjusting Resistor
1. Disconnect A/F sensor connector.




2. Using ohmmeter, measure resistance of adjusting resistor between terminals "R+" and "R-" at A/F sensor connector.
If found faulty, replace A/F sensor.

Adjusting resistor resistance
100 - 58000 Ohms at 20 degrees C (68 degrees F)

3. Connect A/F sensor connector securely.