VOLVO
ECM-24BB - 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:
5 modelsS60 (2001–2009), S80 (1999–2006), V70 (2000–2008), V70 XC / XC70 (2001–2007), XC90 (2003–)
Show models by year and engine (14)
- Volvo S60 (2001–2009)2005–2006Engine B5204T5, B5244T4, B5244T5, B5254T2, B5254T4 only
- Volvo S60 (2001–2009)2007Engine B5204T5, B5244T5, B5254T2, B5254T4 only
- Volvo S60 (2001–2009)2008–2009Engine B5204T5, B5244T5, B5254T2 only
- Volvo S80 (1999–2006)2005–2006Engine B5204T5, B5244T4, B5254T2, B6294S2, B6294T only
- Volvo V70 (2000–2008)2005Engine B5204T5, B5244T4, B5244T5, B5254T2, B5254T4 only
- Volvo V70 (2000–2008)2006–2007Engine B5204T5, B5244T5, B5254T2, B5254T4 only
- Volvo V70 (2000–2008)2008Engine B5254T2 only
- Volvo V70 XC / XC70 (2001–2007)2005All engines except: D5244T
- Volvo V70 XC / XC70 (2001–2007)2006Engine B5244T4, B5254T2 only
- Volvo V70 XC / XC70 (2001–2007)2007Engine B5254T2 only
- Volvo XC90 (2003–)2005–2006Engine B5254T2, B6294T only
- Volvo XC90 (2003–)2007–2012Engine B5254T2 only
- Volvo XC90 (2003–)2013–2014Engine B5254T9 only
- Volvo XC90 (2003–)2015
What does this fault code mean?
Although the code is titled signal missing, it applies when the learned correction values of the two oxygen sensors diverge too far. The engine control module (ECM) compares the two values and stores the code when the deviation is too large. The fault may then lie in the front or rear sensor circuit.
Possible causes
- Leakage in the exhaust system
- Oxygen sensor indicates an incorrectly rich fuel/air mixture
- Contact resistance or oxidation at the connections
- Damaged oxygen sensor
What you can do
- 1Read and note the code, clear it and road test to see whether it returns
- 2Look at the connectors to the front and rear oxygen sensors for contact resistance and oxidation
- 3Look for air leaks in the exhaust system, such as cracks and loose joints
- 4If the fault remains after these checks, have a workshop try replacing the oxygen sensors, since the code can also be set by a damaged front or rear sensor
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.