VOLVO
ECM-24BD - 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:
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?
The engine control module (ECM) compares the front oxygen sensor with the rear one. If the front sensor shows a lean fuel/air mixture while the rear sensor shows a rich one, the code is stored. The fault may lie in the front or rear sensor circuit, and an exhaust leak can also cause it.
Possible causes
- Leakage in the exhaust system
- Oxygen sensor indicates an incorrectly rich fuel/air mixture
- Damaged oxygen sensor
What you can do
- 1Clear the code and road test to see whether it comes back
- 2Check that there are no air leaks in the exhaust system, for example at flanges and the silencer
- 3Look at the oxygen sensor connectors and make sure they are clean and fully seated. Rust solvent spray and grease must not be used
- 4If the fault remains, 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.