VOLVO
ECM-121C - Mass air flow (MAF) sensor. Signal too high
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 measured air mass from the mass air flow sensor is higher than the value the engine control module has calculated, and the code is set. The fault can lie in the wiring, where the signal wire may be shorted to supply voltage or the ground wire broken, or in the sensor itself.
Possible causes
- Signal wire short-circuited to supply voltage
- Open circuit in the ground lead
- Damaged mass air flow sensor
What you can do
- 1Check the wiring to the mass air flow sensor for chafing and loose connectors
- 2Use a multimeter to check that the signal wire has no contact with supply voltage and that the ground wire is not broken
- 3With your own diagnostic tool, check that the air mass in live data rises smoothly when the throttle is pressed
- 4If the fault remains, have a workshop check the mass air flow sensor and its wiring
Symptoms you may notice2
- The malfunction indicator lamp comes on
- The engine runs worse than normal
What the fault can affect3
- Boost pressure is 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.