VOLVO
ECM-121D - Mass air flow (MAF) sensor. 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 measured air mass from the mass air flow sensor is lower than the value calculated by the engine control module, and the code is set when the difference becomes too large. Possible causes are a leak in the intake, poor contact, a wiring fault such as a break or a short to ground, or damage to the sensor itself.
Possible causes
- Air leakage in the intake system
- Contact resistance in the sensor connectors
- Signal wire short-circuited to ground
- Open circuit in the signal wire or power supply
- Damaged mass air flow sensor
What you can do
- 1Check that the intake hoses are sealed, since a leak gives too low a measured air quantity
- 2Check the mass air flow sensor connectors for contact resistance and oxidation
- 3Use a multimeter to check that the signal wire is not shorted to ground or broken, and that the supply is intact
- 4If the fault remains, have a workshop check the mass air flow sensor
Symptoms you may notice2
- The malfunction indicator lamp comes on
- The engine performs worse
What the fault can affect3
- Calculated boost pressure is used instead of a measured value
- 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.