VOLVO
ECM-254B - Front heated oxygen sensor (HO2S), bank 2, heating. 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) heats the front oxygen sensor on bank 2 by pulsing the current to its heating element. With the heating switched off, the sensor should give a signal above a certain value. If the signal is below that value, the code is set.
Possible causes
- Contact resistance and oxidation in the connectors
- Open circuit in the supply from the system relay
- 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 fully engaged and free from oxidation and contact resistance. Do not use rust solvent spray or grease on the connector
- 3Use a multimeter to check that the supply wire from the system relay to the sensor is not open circuit
- 4Look for chafing and breaks in the wires to the sensor, especially where the cable runs close to the exhaust system
- 5If the connectors and wiring are 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.