MAPsensor

MAP sensor, short for manifold absolute pressure sensor, is a device used in internal combustion engines to measure the absolute pressure inside the intake manifold. The ECU (engine control unit) uses the MAP reading to estimate air density and engine load, which informs fuel metering and ignition timing to achieve proper air–fuel ratio, efficiency, and emissions control.

Most MAP sensors are MEMS devices that provide either an analog voltage or a digital signal. Common analog outputs are 0.5 to 4.5 volts or 1 to 5 volts, while modern systems may use I2C or SPI digital interfaces. The sensor measures absolute pressure (not gauge pressure), so it accounts for ambient atmospheric pressure as the reference. In naturally aspirated engines, the manifold pressure varies with throttle position and RPM, while in turbocharged or supercharged engines the sensor must tolerate higher pressures.

Placement and operation typically involve a pressure port connected to the intake manifold, sometimes through a vacuum line. The ECU combines MAP data with engine speed (RPM) and other inputs to estimate air mass flow, determine fueling, and adjust ignition timing. In many engines, the MAP sensor is used in conjunction with or as an alternative to a mass airflow sensor (MAF).

Common failure symptoms include rough idle, poor acceleration, inconsistent engine behavior, or a check engine light. Causes can include vacuum leaks, clogged ports, sensor contamination, or wiring faults. Replacement requires matching the pressure range, electrical interface, and connector layout to the vehicle’s specifications; some systems may require ECU relearn or calibration after replacement.