GM Caprice 1990-1993 Repair Guide

Manifold Absolute Pressure (MAP) Sensor


See Figure 1

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Fig. Fig. 1: Manifold Absolute Pressure (MAP) sensor


The MAP sensor measures the changes in intake manifold pressure, which result from engine load and speed changes and converts this information to a voltage output. The MAP sensor reading is the opposite of a vacuum gauge reading: when manifold pressure is high, MAP sensor value is high and vacuum is low. A MAP sensor will produce a low output on engine coastdown with a closed throttle while a wide open throttle will produce a high output. The high output is produced because the pressure inside the manifold is the same as outside the manifold, so 100 percent of the outside air pressure is measured.

The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the ECM to automatically adjust for different altitudes.

The MAP sensor changes the 5 volt signal supplied by the ECM, which reads the change and uses the information to control fuel delivery and ignition timing.


  1. Disconnect the negative battery cable.
  3. Disconnect the vacuum harness assembly.
  5. Release the electrical connector locking tab.
  7. Remove the bolts or release the MAP sensor locking tabs and remove the sensor.

To install:
  1. Install the bolts or snap sensor onto the bracket.
  3. Connect the MAP sensor electrical connector.
  5. Connect the MAP sensor vacuum harness connector.
  7. Connect the negative battery cable.