VOLVO
ECM-232B - Rear heated oxygen sensor (HO2S), 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) follows the signal from the rear oxygen sensor on bank 2. The code is set when the signal disappears or moves outside its range, or when the heating of the sensor disturbs it. Meanwhile, control of the oxygen sensor after the catalytic converter is switched off.
Possible causes
- Poor contact or oxidation in the sensor connector
- Open circuit in the signal wire
- Open circuit in the ground wire
- Damaged rear oxygen sensor
What you can do
- 1Read the code, clear it and road test to see whether it returns
- 2Look at the connector to the sensor on bank 2 and check it for oxidation or play
- 3Use a multimeter to check that the signal and ground wires to the sensor have no break
- 4If you have a diagnostic tool: watch the sensor signal in live data while the engine runs and confirm that it moves
- 5If the fault remains, have a workshop decide whether a new rear oxygen sensor is needed
Symptoms you may notice1
- Malfunction indicator lamp (MIL) lit
What the fault can affect2
- Oxygen sensor control after the catalytic converter is switched off
- Catalytic converter diagnostics are switched off
General guidance for car owners. Diagnosis on the car can point to a different cause.