VOLVO
ECM-121B - Mass air flow (MAF) sensor. Flow 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 air mass correction value has become too low, while the long-term fuel adjustment lies outside its normal range. The measured air quantity is therefore lower than the calculated one, and the engine may run poorly.
Possible causes
- Oxidation or contact resistance in the mass air flow connectors
- Air leakage in the intake system
- Blocked intake system
- Damaged mass air flow sensor
What you can do
- 1Check the mass air flow sensor connector for contact resistance and oxidation
- 2Check that the hoses between the mass air flow sensor and the throttle unit are secure and sealed
- 3Look inside the throttle housing for dirt and clean it if needed
- 4Clear the code and road test
- 5If the fault remains after these checks, have a workshop check or replace the mass air flow sensor
Symptoms you may notice2
- Malfunction indicator lamp on
- The engine runs worse than normal
What the fault can affect3
- Boost pressure and air mass are calculated instead of measured
- Rear oxygen sensor control is switched off
- Misfire detection is switched off
General guidance for car owners. Diagnosis on the car can point to a different cause.