HO2S Heater Control Circuit (Bank 1 Sensor 2)
The rear lambda sensor, after the catalyst, also has a heater so it can read.
What the car has detected
The ECU does not see the right current in the rear sensor’s heater: it is usually open or has a loose wire.
It is not dangerous and the car drives the same, but the catalyst monitoring does not work and it may fail the inspection. Have it checked when you can.
Symptoms
- Engine warning light on
- May fail the emissions test
Possible causes
- Open lambda sensor heater
- Broken or shorted wire, or a loose or corroded connector
- Blown fuse
Checks for the garage
- Measure the sensor heater resistance
- Check the sensor wiring and connector
Next step
Ask for the rear lambda sensor heater and its wiring to be measured.
You can keep using the car and book a visit without hurry.