General Information - More Sensors


A number of sensors provide information to your vehicle's on-board computer or PCM (Powertrain Control Module). The PCM and sensors work together to monitor engine components to achieve optimum performance, efficiency and fuel economy. The PCM is also connected to a variety of "output actuators" - mechanical devices - which respond to the conditions that the sensors monitor. These include the fuel injectors, ignition coils, and various relays and solenoids.

Below are a number of examples of the different types of sensors inside your vehicle.

Note: this is a general description. Consult a repair manual written specifically for your car, truck, van or SUV for exact descriptions.

The Manifold Absolute Pressure (MAP) sensor is located on the intake manifold. It monitors the vacuum or pressure downstream from the throttle plate, inside the intake manifold. This sensor converts the pressure reading to an electrical signal. The PCM then uses this data to determine engine load so it can alter fuel enrichment and ignition advance.

The Mass Air Flow (MAF) sensor is the means by which the PCM measures the amount of air intake the engine draws into the engine.

The Output Shaft Speed (OSS) sensor is located in the automatic transaxle. The OSS sensor provides the PCM with information about the rotational speed of the output shaft in the transmission. The PCM uses this information to control the torque converter, to calculate speed scheduling, and the correct operating pressure that the transaxle requires.

Oxygen sensors generate an electrical voltage signal that shows the difference between the oxygen content in the exhaust system and the oxygen content in the outside air. The PCM uses this signal to maintain the proper air/fuel ratio in the ignition system by constantly adjusting the "on time" of the fuel injectors. The number of oxygen sensors in your engine depends on engine size.

The Throttle Position (TP) sensor sends the PCM a signal that tells it the "open" angle of the throttle plate inside the throttle body: the signal tells the PCM when the throttle is closed, half-open, wide open or anywhere in between. The PCM uses this information, along with data from other sensors, to calculate fuel injector on or off time.

The Transmission Range (TR) switch prevents the engine from starting in any gear other than Park or Neutral. The PCM uses data from the TR to determine which gear has been selected and the correct pressure for the transaxle's electronic pressure control system.