Theory Of Operation

The Powertrain Control Module (PCM) uses the Manifold Absolute Pressure (MAP) Sensor base model and the Electronic Throttle Control (ETC) Motor position value to create a calculated MAP model value. This calculated MAP model is then compared to the actual MAP Sensor Signal input to the PCM. The PCM uses this comparison to detect vacuum leaks or restrictions in the intake air system. The purpose of this monitor is to detect an instantaneous or gradual change in the intake manifold vacuum that exceeds the calibrated high or low thresholds.