How to Test a Manifold's Absolute Pressure Map Sensor

by Don Bowman
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The manifold absolute pressure sensor, or MAP sensor, is generally used in place of the mass airflow sensor in an automobile. It preceded the mass airflow sensor and was much less efficient. The MAP sensor measures the pressure in the intake manifold through a vacuum. The more pressure, the lower the vacuum and the lower the voltage output. The lower the pressure, the higher the vacuum and the higher the voltage output signal. The mass airflow measures the volume of air moving into the manifold.

Step 1

Connect the voltmeter to the MAP sensor by connecting the black lead to a good ground and connecting the red lead to the center of the three wires in the MAP sensor's electrical connector.

Step 2

Turn the ignition key on with the engine off. The voltage displayed on the voltmeter should be between 4.5 to 5 volts.

Step 3

Start the engine and the voltage displayed should be .5 to 1.5 volts at sea level or close. The voltage will decrease as altitude increases. If the voltage differs greatly on either test, the MAP sensor is fried. Replace it.

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