VOLVO
ECM-250B - 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?
Although the code is titled signal missing, it applies when the heater element of the front oxygen sensor on bank 2 has gone without control for a certain amount of time. The engine control module then stores the code.
Possible causes
- Contact resistance and oxidation at the connections
- Damaged front heated oxygen sensor
What you can do
- 1Read and note the code, clear it and road test to see whether it returns
- 2Check the connector to the front oxygen sensor on bank 2 for oxidation and loose connections. Do not use rust solvent spray or grease in it
- 3If possible, take readings from the cable side of the connector so it is not damaged and does not become a loose contact later
- 4If the connector is clean but the fault remains, have a workshop try a new front oxygen sensor
Symptoms you may notice1
- The malfunction indicator lamp (MIL) is lit
General guidance for car owners. Diagnosis on the car can point to a different cause.