VOLVO
ECM-24CB - Front heated oxygen sensor (HO2S), bank 1. Signal missing
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?
Although the code is titled signal missing, it applies when the front and rear sensors give conflicting pictures of the mixture, or when the front signal deviates too much from what the engine control module expects. The fault can then lie in either sensor or in their circuits.
Possible causes
- Leakage in the exhaust system
- Front sensor shows an overly rich mixture
- Contact resistance or oxidation in the connectors
- Damaged oxygen sensor
What you can do
- 1Read and note the code, clear it and road test to see whether it comes back
- 2Make sure the connectors to the front and rear oxygen sensors are clean, firmly seated and free from oxidation
- 3Look for air leaks in the exhaust system, especially upstream of the front sensor
- 4If there is no leak, have a workshop with diagnostic equipment 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.