A/F Sensor On-Vehicle Inspection

A/F Sensor Heater

1)Disconnect negative (–) cable at battery.

2)Disconnect A/F sensor connector.

3)Using ohmmeter, measure resistance between terminals “Heater +” and “Heater –” at sensor connector (1).
If resistance is not as specified, replace A/F sensor.

NOTE:

Ambient temperature of sensor affects resistance largely. Check sensor heater is at reference temperature.

A/F sensor heater resistance

2.4 to 4.0 Ω at 25 °C (77 °F)