Troubleshooting a Mass Air Flow Sensorby John Albers
What is a Mass Air Flow Sensor?
A Mass Air Flow Sensor works in conjunction with a vehicle's oxygen sensor to send signals to the ECM or Engine Control Module. While the oxygen sensor tells the ECM how much oxygen is passing through the engine, the Mass Air Flow Sensor tells the engine how much air overall is moving through the engine. With this information, the ECM can control the vehicle's fuel injectors to change the fuel/air ratio going into the engine.
Signs and Symptoms of a Problem With a Mass Air Flow Sensor
The Mass Air Flow Sensor may have problems if the vehicle experiences a sudden loss of power, hesitates upon acceleration, the engine knocks and pings, and gets poor gas mileage. Depending on whether the Mass Air Flow Sensor is broken or simply obstructed, the check engine light may or may not be lit.
Troubleshooting a Mass Air Flow Sensor
First find the Mass Air Flow Sensor. They are mounted in different spots depending on the model of vehicle one is dealing with. They're most often found on an intake or exhaust pipe, a small box with a wire threaded down into the pipe. Remove the box and take out the wire, being careful not to touch it directly with the fingers. It's possible that the wire has become coated with grease, oil or some other debris, which is preventing it from getting an accurate air flow reading. Clean the wire off with a mild solvent, rinse it with water, and then dry it with a clean cloth, before replacing it. Should the check engine light be on, you will need an engine code scanner. This device plugs into a jack located in or near the driver side fuse box. If the engine codes include: P0171, P0172, P0174, P0175, then the Mass Air Flow Sensor is not working and needs to be replaced. If the scanner displays any other code, then it's a problem not related to the Mass Air Flow Sensor and should be seen by a mechanic.