VOLVO
ECM-231B - Rear heated oxygen sensor (HO2S), aging, bank 2. Signal missing
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
2 modelsS80 (1999–2006), XC90 (2003–)
Show models by year and engine (2)
What does this fault code mean?
The engine control module (ECM) monitors the rear oxygen sensor on bank 2 by checking its signal. The code is set when the module registers no signal at all from the sensor. The fault is most often caused by a sensor that has worn out or aged.
Possible causes
- Damaged rear oxygen sensor, often due to age and wear
What you can do
- 1Read the code, clear it and road test to see whether it comes back
- 2Check that the connector to the rear oxygen sensor on bank 2 is secure and clean
- 3Do not use rust solvent spray or grease on the sensor connector
- 4Check the exhaust system for leaks, since air getting in there can affect the sensor signal
- 5If the checks find nothing, have a workshop decide whether a new rear oxygen sensor is needed
Symptoms you may notice1
- Malfunction indicator lamp (MIL) lit
General guidance for car owners. Diagnosis on the car can point to a different cause.