VOLVO
ECM-255D - Front heated oxygen sensor (HO2S), bank 2. Signal too low
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 oxygen sensor on bank 2 is controlled by the engine control module (ECM), and an internal fault has occurred there. The code concerns a signal that is too low, but the fault lies in the control module. If the fault returns despite checks, the control module needs replacing.
Possible causes
- Damaged engine control module (ECM)
What you can do
- 1Read the code, clear it and road test the car to see whether it returns
- 2Check that the battery is in good condition and that its terminals are tight
- 3Check that the connectors to the engine control module are fully engaged and free from oxidation
- 4Have a workshop replace the engine control module if the fault returns
Symptoms you may notice1
- Malfunction indicator lamp (MIL) on
General guidance for car owners. Diagnosis on the car can point to a different cause.