The Manifold Absolute Pressure (MAP) sensor serves as a Powertrain Control Module (PCM) input, using a silicon based sensing unit, to provide data on the manifold vacuum that draws the air/fuel mixture into the combustion chamber. The PCM requires this information to determine injector pulse width and spark advance. When MAP equals Barometric pressure, the pulse width will be at maximum.
Also like the cam and crank sensors, a 5 volt reference is supplied from the PCM and returns a voltage signal to the PCM that reflects manifold pressure. The zero pressure reading is 0.5 volt and full scale is 4.5 volt. For a pressure swing of 0 - 15 psi the voltage changes 4.0 volt. The sensor is supplied a regulated 4.8 to 5.1 volts to operate the sensor. Like the cam and crank sensors ground is provided through the sensor return circuit.
Removal & Installation
- Remove the air intake assembly.
- Disconnect the negative battery cable.
- Disconnect the electrical connector from the Manifold Absolute Pressure (MAP) sensor.
- Remove the mounting screw from the MAP sensor and remove the sensor.
- Install the MAP sensor to the intake manifold and tighten the screw.
- Connect the electrical connector to the MAP sensor.
- Connect the negative battery cable.
- Install the air intake assembly.
- Turn the ignition off.
- Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the MAP Sensor and the PCM.
- Look for any chafed, pierced, pinched, or partially broken wires.
- Look for broken, bent, pushed out or corroded terminals.
- Turn the ignition on.
- Monitor the scan tool data relative to the sensor and wiggle test the wiring and connectors.
- Look for the data to change or for a DTC to set during the wiggle test. If necessary, check each sensor circuit for high resistance or a shorted condition.
- With a scan tool, read the Barometric Pressure. The Barometric Pressure should be approximately equal to the actual barometric pressure. If necessary, compare the Barometric Pressure value of the tested vehicle to the value of a known good vehicle of a similar make and model.
- Connect a vacuum gauge to a manifold vacuum source and start the engine.
- With the scan tool, read the MAP Sensor vacuum. The scan tool reading for MAP vacuum should be within 1 inch of the vacuum gauge reading.
- With the scan tool, monitor the MAP Sensor signal voltage. With the engine idling in neutral or park, snap the throttle. The MAP Sensor signal voltage should change from below 2.0 volts at idle to above 3.5 volts at wide open throttle.