DTC P1128: Manifold Absolute Pressure (MAP) Sensor Signal Lower Than Expected: General Description

The manifold absolute pressure (MAP) sensor senses manifold absolute pressure (vacuum) and converts it into electrical signals. The MAP sensor outputs low signal voltage at high vacuum (idling) and high signal voltage at low vacuum (throttle valve wide open). The engine control module (ECM)/powertrain control module (PCM) compares a predetermined MAP value at a given throttle position and manifold absolute pressure to the output voltage value of the MAP sensor. If the MAP sensor outputs lower voltage than expected, the ECM/PCM detects a malfunction and stores a DTC.