VOLVO
ECM-254C - Front heated oxygen sensor (HO2S), bank 2, heating. Signal too high
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) heats the front oxygen sensor on bank 2 by pulsing the current to its heating element. While the heating is active, the sensor signal should stay below a certain value. If the signal is above that value, the code is set.
Possible causes
- Signal wire short-circuited to supply voltage
- Damaged front oxygen sensor on bank 2
What you can do
- 1Read the code, clear it and road test the car to see whether it returns
- 2Check that the lambda sensor connector is clean and fully engaged. Do not use rust solvent spray or grease on it
- 3Use a multimeter to check that the signal wire has no voltage to ground when the control module is disconnected
- 4Look for chafing and places where the signal wire may have been pinched or worn against a sharp edge
- 5If the wire is intact the sensor may be damaged; have a workshop check it or replace it
Symptoms you may notice1
- Malfunction indicator lamp (MIL) on
What the fault can affect1
- Oxygen sensor control is switched off
General guidance for car owners. Diagnosis on the car can point to a different cause.