Manifold Pressure/Vacuum Sensor: Description and Operation

MANIFOLD ABSOLUTE PRESSURE SENSOR (MAP)





The MAP (manifold absolute pressure) sensor provides a voltage proportional to the absolute pressure in the intake manifold. This signal allows the load on the engine to be calculated and used within the internal calculations of the ECM (engine control module). The sensor is located on the rear of the air intake manifold.

Pin No Description
1 MAP (manifold absolute pressure) signal
2 Sensor supply
3 Not used
4 Sensor ground

The output signal from the MAP (manifold absolute pressure) sensor, together with the CKP (crankshaft position) and IAT (intake air temperature) sensors, is used by the ECM (engine control module) to calculate the amount of air induced into the cylinders. This enables the ECM (engine control module) to determine ignition timing and fuel injection duration values.

The MAP (manifold absolute pressure) sensor receives a 5V supply voltage from pin 48 of ECM (engine control module) connector C0634 and provides an analogue signal to pin 69 of ECM (engine control module) connector C0634, which relates to the absolute manifold pressure and allows the ECM (engine control module) to calculate engine load. The ECM (engine control module) provides a ground for the sensor via pin 11 of ECM (engine control module) connector C0634.

If the MAP (manifold absolute pressure) signal is missing, the ECM (engine control module) will substitute a default manifold pressure reading based on crankshaft speed and throttle angle. The engine will continue to run with reduced drivability and increased emissions, although this may not be immediately apparent to the driver. The ECM (engine control module) will store fault codes which can be retrieved using T4.