Wells Vehicle Electronics' Manifold Absolute Pressure Sensors are designed and manufactured to meet or exceed original equipment manufacturers' specifications for performance and durability. The Manifold Absolute Pressure Sensor, also known as the MAP sensor, measures atmospheric pressure inside the intake manifold and sends a voltage signal to the Engine Control Module (ECM). As atmospheric pressure inside an intake manifold is negative during vehicle operation, the sensor is actually measuring vacuum. The ECM calculates proper air/fuel ratios, idle speeds, and ignition spark timing based in part on the Manifold Absolute Pressure Sensor's signal. A malfunctioning or inoperative Manifold Absolute Pressure Sensor can cause drivability symptoms such as hard starting, stalling, harsh or poor transmission shift points, rough idle, and hesitation. It can also cause the Check Engine Light (CEL), Service Engine Soon (SES), or Malfunction Indicator Lamp (MIL) to illuminate and can set a trouble code (P-code) in the ECM when not functioning correctly. Not correcting a failed Manifold Absolute Pressure Sensor condition can cause reduced fuel mileage and performance, increased emissions, and damage to other components such as the catalytic converter.