How to Test the Mass Air Flow Sensor in a Nissan Truckby Cayden Conor
The mass air flow (MAF) sensor in a Nissan truck sends a signal to the truck's computer. As the intake air increases, the voltage from the MAF sensor increases. The truck's computer uses this signal to determine engine load and adjusts ignition timing and fuel timing for optimum engine performance. If the MAF sensor fails, the computer will go into "limp home" mode and will not allow the engine to run higher than 3,000 rpm.
Locate the MAF sensor. Depending on the year and model Nissan truck, the sensor could be located in the air duct or anywhere on the engine block. The MAF connector is on the sensor. When you're facing the sensor, the left-most wire is the ignition wire, the center wire is the ECM, or computer signal wire, and the right-most wire is the MAF signal wire.
Set a voltmeter to volts. Stick a pin or needle into the MAF signal wire. Attach the voltmeter's red lead to the pin. Attach the black lead to a good ground such as the engine block or engine lift-hook. Have an assistant start the vehicle and accelerate the engine slowly. Watch the voltmeter. As the rpm increases, the voltage should increase. The voltage increase should be smooth with no jumps or stutters. If the MAF sensor fails this test, replace the sensor.
Have your assistant push hard on the gas pedal then release it. The voltmeter should show an initial rise and drop, then another rise in voltage. If the MAF sensor fails this test, replace the sensor.
Turn off the engine. Move the pin to the ignition wire. Attach the voltmeter's red lead to the pin. Leave the black lead on the ground. Turn the ignition key on, but leave the engine off. Voltage should be battery voltage, or between 12.0 and 13.5 volts. If the MAF sensor fails this test, replace the sensor.
Start the vehicle again. Voltage should be battery voltage or a little higher with the engine running, or between 13.5 and 14.5 volts. If the MAF sensor fails this test, replace the sensor.