O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
What it means
The downstream sensor sits after the catalytic converter to monitor it, and like the upstream sensor it has a built-in heater. This code means that heater circuit is not working correctly, most often because the heater has burned out.
Symptoms
- Check engine light on.
- Usually no noticeable effect on performance.
- The computer may be unable to test converter efficiency.
Possible causes
- Burned-out downstream sensor heater.
- Blown heater fuse.
- Wiring damaged by road debris and water under the car.
- Corroded connector.
How to diagnose and fix
- Check the fuse for the oxygen sensor heaters.
- Inspect the wiring under the car for breaks or chafing.
- Clean the connector and make sure it is secure.
- Measure heater resistance and replace the sensor if out of specification.
Repair cost
A downstream sensor is often cheaper than the upstream one, keeping the cost low to moderate.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Frequently asked questions
Should I also replace the upstream sensor?
Not necessarily. This code concerns only the downstream sensor; replace the upstream one only if it has its own code or a weak signal.
Does it affect fuel economy?
Very little, since the downstream sensor plays only a minor role in fueling, but it keeps the check engine light on.
This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.
Report a mistake
Spotted something inaccurate? Tell us and we will review and correct it.