VOLVO
ECM-254D - Front heated oxygen sensor (HO2S), bank 2, heating. 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 front oxygen sensor on bank 2 has an electric heater that the engine control module (ECM) controls with pulsed current. With the heating switched off, the signal should not fall below a certain value. If the ECM sees a signal that is too low in that state, the code is set.
Possible causes
- Signal wire short-circuited to ground
- 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 connector at the lambda sensor is fully engaged and free from moisture and oxidation. Do not use rust solvent spray or grease in the connector
- 3Use a multimeter to check that the signal wire has no contact with ground (chassis) when it is disconnected from the control module
- 4Look for chafed spots on the signal wire, where it may have been pinched or rubbed against a hot or sharp edge
- 5If the wire is intact and the connector is good 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.