VOLVO
ECM-233D - Rear 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 engine control module (ECM) controls the heating of the rear oxygen sensor on bank 2. The code is set when the signal is too low while heating is switched off. The signal wire may be in contact with ground, and a damaged sensor can also set the code.
Possible causes
- Signal wire short-circuited to ground
- Damaged oxygen sensor
What you can do
- 1Read and clear the code, then road test to see whether it returns
- 2Inspect the signal wire for chafing or spots where it may have touched the body
- 3With the sensor connector unplugged, use a multimeter to check whether the signal wire is in contact with ground
- 4If you have a diagnostic tool: see whether the sensor signal sits low and does not move while the engine runs
- 5If the fault remains, have a workshop decide whether the sensor should be replaced
Symptoms you may notice1
- Malfunction indicator lamp (MIL) lit
What the fault can affect1
- Lambda control is switched off
General guidance for car owners. Diagnosis on the car can point to a different cause.