Reads a change in manifold pressure. The computer uses this information to adjust timing advance and air/fuel ratio.
The EMS uses the MAP sensor on systems that have a Mass Airflow Sensor (MAF) as a backup. The EMS also uses the MAP sensor as an EGR diagnostic device and as an engine load verification device. The EMS system uses this information to calculate engine load and EGR flow rates. The EMS uses speed-density calculations (non-mass airflow sensor systems) to determine the required amount of fuel delivery.