VOLVO
ECM-24CD - Front heated oxygen sensor (HO2S), bank 1. Signal too low
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
4 modelsC30 (2007–2013), C70 (2006–2013), S40 (2004–2013), V50 (2004–2013)
Show models by year and engine (9)
- Volvo C30 (2007–2013)2007Engine B5254T3 only
- Volvo C30 (2007–2013)2008–2013Engine B5254T7 only
- Volvo C70 (2006–2013)2006–2007Engine B5254T3 only
- Volvo C70 (2006–2013)2008–2013Engine B5254T7 only
- Volvo S40 (2004–2013)2005–2007Engine B5254T3 only
- Volvo S40 (2004–2013)2008Engine B5254T3, B5254T7 only
- Volvo S40 (2004–2013)2009–2012Engine B5254T7 only
- Volvo V50 (2004–2013)2005–2007Engine B5254T3 only
- Volvo V50 (2004–2013)2008–2012Engine B5254T7 only
What does this fault code mean?
The ECM checks the front oxygen sensor against the rear one and checks both against their learned correction values. If the front sensor shows a rich mixture while the rear one shows a lean one, or the values drift too far apart, the code is stored. The fault can lie in the front or rear sensor circuit.
Possible causes
- Leakage in the exhaust system
- Oxygen sensor gives an incorrectly rich signal
- Damaged oxygen sensor
What you can do
- 1Clear the code and road test to see whether it returns
- 2Check that there is no air leak in the exhaust system, for example at flanges and the silencer
- 3Make sure the oxygen sensor connectors are clean and fully seated
- 4If the fault remains, have a workshop try replacing the oxygen sensors, since a damaged front or rear sensor can also cause the fault
Symptoms you may notice1
- The malfunction indicator lamp (MIL) is lit
What the fault can affect2
- Oxygen sensor control is switched off
- Catalytic converter diagnostics are switched off
General guidance for car owners. Diagnosis on the car can point to a different cause.