Manifold Absolute Pressure (MAP) Sensor

MAP sensor is connected to ECM by a 3-wire harness and to engine by a manifold vacuum hose. ECM applies a 5-volt reference signal from ECM terminal A23 to MAP sensor. MAP sensor has an internal mechanical resistor which varies resistance based on changes in engine load (manifold vacuum). As internal resistance varies, return voltage signal varies at ECM terminal A22. ECM interprets this voltage change as changes in engine load and uses this signal to help determine control of fuel injectors, Idle Air Control (IAC) valve and EGR system.