VOLVO
ECM-252D - Front heated oxygen sensor (HO2S), bank 2. 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 front oxygen sensor on bank 2 reacts too slowly to changes in the exhaust gases. The ECM checks how well the sensor has aged and stores the code when its reaction has become too sluggish.
Possible causes
- Calibration current and pump current cables short-circuited to each other
- Open circuit in the signal cable (-)
- Open circuit in the cable for calibration current
- 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 at the oxygen sensor on bank 2 for oxidation and loose connections. Rust solvent spray and grease must not be used
- 3Use a multimeter to check that the signal cable and the calibration current cable have no open circuit and are not short-circuited to each other
- 4Follow the cables from the sensor and look for chafing and pinch damage, especially near the exhaust pipe
- 5If the cables are intact, have a workshop with diagnostic equipment check the oxygen sensor
Symptoms you may notice1
- The malfunction indicator lamp (MIL) is lit
What the fault can affect1
- Catalytic converter diagnostics are switched off
General guidance for car owners. Diagnosis on the car can point to a different cause.