OPERATION
This sensor advises the ECM of pressure changes in the intake manifold. It consists of a semi-conductor pressure converting element which converts a pressure change into an electrical signal. The ECM sends a reference signal to the MAP sensor; the change in air pressure changes the resistance within the sensor. The ECM reads the change from its reference voltage and signals its systems to react accordingly.
TESTING
See Figures 1, 2, 3 and 4
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Fig. Fig. 1: Wiring schematic of the Manifold Absolute Pressure (MAP) sensor circuit
Use only a 10 megaohm digital multi-meter when testing. The use of any other type of equipment may damage the ECM and other components.
- Unplug the vacuum sensor connector.
- Turn the ignition switch ON.
- Using a voltmeter, measure the voltage between terminals VCC and E2 of the vacuum sensor connector. It should be between 4-6 volts.
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Fig. Fig. 2: Using a voltmeter, measure the voltage between the MAP connector terminals
- Turn the ignition switch OFF.
- Push the electrical connector back into place.
- Disconnect the vacuum hose from the sensor.
- Connect the voltmeter to terminals PIM and E2 of the ECM. Measure and record the output voltage under ambient atmospheric pressure.
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Fig. Fig. 3: Connect the voltmeter to terminals PIM and E2 of the ECM
- Apply vacuum to the sensor according to the segments show on the chart. Measure each voltage drop and compare to the chart.
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Fig. Fig. 4: Manifold Absolute Pressure (MAP) sensor voltage drop specifications
- Reconnect the vacuum hose to the MAP sensor.
REMOVAL & INSTALLATION
Replacing the MAP sensor simply requires unplugging the vacuum and electrical connections, then unbolting the sensor. Inspect the vacuum hose over its entire length for any signs of cracking or splitting. The slightest leak can cause false messages to be send to the ECM.