How to Test a Ford Mass Air Flow Sensorby Jeremy Holt
A Mass Airflow -- MAF -- Sensor in a modern Ford vehicle is located inside the air intake duct. It uses a hot wire element to measure the amount of air entering the engine. The element is cooled as air passes over it, and this information is converted into an electronic pulse to be relayed to the on-board computer, which can then calculate fuel injection functions. If you suspect a malfunction in this system, check both the MAF sensor and its power supply.
Check the MAF Sensor is Receiving Voltage
Turn the ignition on but do not start the engine. Raise the vehicle's hood and prop it open. Locate the MAF sensor's electrical connector on the air intake duct in the front, center of the engine.
Disconnect the electrical connector from the MAF sensor. On the harness side of the connector attach the negative probe of a voltmeter into the terminal marked GND. Attach the positive probe into the terminal marked B+. If voltage is not recorded there is a disconnect between the battery and sensor harness.
Reconnect the electrical connector into the MAF sensor. Use straight-pins to back-probe the terminals marked SIG and GND; insert the pin into the back to the connector until it contacts the desired terminal. Connect the positive probe of a voltmeter onto the pin in the terminal marked SIG, and the negative probe to the pin in the GND terminal.
Have an assistant start the engine and allow it to idle. The voltmeter should record between 0.2 and 1.5 volts. Raise the engine speed. If the MAF electrical connector is functioning there should be a steady fluctuation in the signal voltage up to around 2 volts.
Check the MAF Sensor
Turn the engine and ignition off. Disconnect the electrical connector from the MAF sensor.
Attach the positive probe of an ohmmeter to the terminal on the MAF marked SIG, and the negative probe to the terminal marked GND.
Take a reading from the ohmmeter -- damage to the hot wire element will be indicated by an open circuit.
Items you will need
- "Haynes Repair Manual: Ford Pick-ups, 1997 - 2003; Expedition 1997 - 2009"; Jay Storer and John H. Haynes; 2009
- Weber State University: Back-Probing Terminals
- The Readout image by Cinneman from Fotolia.com