If your check engine light is on and your Volvo is experiencing some trouble running, it may be time for a new Mass Air Flow Sensor. The Mass Air Flow Sensor is responsible for metering the amount of air entering the engine so it can in turn report back to the ECM (engine control module) and accurately gauge the amount of air coming in so that it can match it with the appropriate amount of fuel. The most common type of Mass Air Flow sensor is the hot wire type which uses a heated wire that is suspended in the MAF air stream with either a constant voltage to the wire or a constant electrical current.
How It Works:
As the wire temperature increases, so does its resistance, and thus varies the electrical current flowing through the circuit. When fresh air flows past the wire it then cools it which decreases its resistance allowing more current to flow through the circuit. The more current flowing, the more the wire's temperature increases, and the increase and decrease is proportional to the amount of air flowing past the wire. This value is then calculated and sent back to the ECM.
Why The Hot Air Type?
The hot wire system in my opinion is the best as it factors in air density, not just volume. If air volume stays the same but temperature or atmospheric pressure changes, the hot wire can sense this by the difference in temperature or current flow.
Mass Air Flow Sensor Failure Symptoms:
- Check engine light illuminated with OBD codes related to MAF sensor faults
- Engine has rough idle and/or stalls
- Short term fuel trim is rich at idle or lean under load
- Constantly runs rich or lean
You can learn how to replace the MAF in your P2 chassis Volvo by watching the following video:
This was installed on a 2004 S60 2.5T however the essential information is the same for the following P2 Chassis models:
- 1999-2006 S80
- 2001-2007 V70
- 2001-2009 S60
- 2003-2007 XC70
- 2003-2014 XC90