How to Service Toyota Mass Air Flow Sensors

by Chris Stevenson
itstillruns article image
Motor - Hot Rod image by Jeffrey Zalesny from

The mass air flow sensor determines the amount of air the engine receives. The mass air flow sensor also sends a command to the vehicle computer, instructing it on how much fuel has to be injected into the engine. Some common problems with the sensor can be the vehicle stalling during cold operation, sluggish acceleration, spark plug misfiring and erratic fuel economy. The first indication that a sensor has malfunctioned might be a "check engine soon" dashboard light. A general inspection and repair of the of the mass air flow sensor can be performed by the average do-it-yourself repair person, without replacing the unit.

Step 1

Place the vehicle in park or neutral with the emergency brake engaged. Raise the hood. Disconnect the negative battery cable at its post. Locate the mass air flow sensor housing; it will sit near the air cleaner. It's about the size of a cigarette box and forms a connection between the air intake and the throttle body.

Step 2

Remove the small electrical connector jack from the mass air flow sensor. Look at the inside of both connector junctions—you will see prongs and inlet receptacles. Use the electrical spray to clean both connector points, allowing full spray pressure. Use Q-tips to remove excessive debris from the connector points. Reconnect the electrical connection jack at this time, if you wish.

Step 3

Use a Phillips screwdriver to remove the screws that secure the mass air flow sensor to its mount. Spray the electrical cleaner at full pressure inside the device. Saturate the area that holds the two platinum sensor wires; these contacts comprise the heat temperature sensor and the intake air thermistor. Clean them with the electrical spray and Q-tips until they have regained their shiny appearance. Make certain they have not broken or become bent. Carefully clean any orifice or other electrical connection point inside the housing. Use a small amount of steal wool on both sensors if they have become heavily oxidized and soot-encrusted. Be careful not to apply too much cleaning pressure on the sensors.

Reinstall the mass air flow sensor onto its mount, tightening the two Phillips screws with the screwdriver.

Step 4

Open the air cleaner housing by unscrewing the wing nut or bolt, if the vehicle has a standard, or old-style, housing. If the vehicle has an air intake box assembly, release the retaining clips or screws that hold it in place. Remove the old air cleaner element and replace it with a new one. If the vehicle has a PCV fiber filter located on the inside of the air cleaner housing, slide the U-clip free and replace the small fiber filter. Reconnect the negative battery cable to its post. Start the engine. Shut the engine off and wait for 10 seconds. Start the engine again; this should reset the computer and extinguish any service engine soon light. Test drive the vehicle.

More Articles

article divider