VOLVO
ECM-250D - 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 engine control module (ECM) checks the resistance in the preheating circuit of the front oxygen sensor on bank 2. If the resistance is too low, the code is stored. The fault can lie in the heater wiring or in the sensor itself.
Possible causes
- Short circuit in the preheating circuit
- Damaged front heated oxygen sensor
What you can do
- 1Read and note the code, clear it and road test to see whether it returns
- 2Follow the heater wiring from the bank 2 oxygen sensor and look for chafing, damage and places where the wires may have touched each other
- 3Look at the sensor connector. Rust solvent spray and grease must not be used on it
- 4If the wiring is intact, 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.