- 1). Attach the voltmeter's red lead to the MAF signal wire, which is the second wire from the left. Attach the voltmeter's black lead to a know good ground. Turn the key on, but do not start the vehicle. The voltage should be between 1.5 to 1.6 volts. Start the vehicle. As the vehicle warms up, the voltage should be 2.5 to 2.9 volts (warm idle). At 2,500 rpm, the voltage should be 3.0 to 3.5 volts.
- 2). Open the throttle slowly and watch the voltage. The voltage should increase with the increase in rpm. It should not have any drop outs. Bring the throttle back down to an idle.
- 3). Snap the throttle wide open and close is as fast as possible. The voltage should rise and drop -- if not, the MAF is not reacting to changes in the air flow fast enough and should be replaced.
- 4). Complete the out of range signal test if the previous test shows no voltage. Connect the red voltmeter lead to the second wire from the right -- on the connector -- which is the ignition wire. Connect the voltmeter's black lead to a known good ground. You should see battery voltage -- 12.5 to 13.5 volts on the voltmeter, with the engine off.
- 5). Start the vehicle. The voltage should be charging battery voltage -- between 13.5 and 14.5 volts. If voltage is present, disconnect the voltmeter's red lead from the ignition wire. Attach it to the ECM wire -- the third wire from the right. Leave the black wire on a known good ground. Voltage should be 0.010 volts. If not, replace the MAF sensor.
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