Throttle Position Sensors (TPS) are the only sensor in the Engine Management System (EMS) that the vehicle operator has direct control. The sensor is a potentiometer providing an analog signal to the computer. This signal represents how far the throttle plates have opened.
Engine Management Systems calculate how much air should have entered the engine and compares this value with the Manifold Absolute Pressure (MAP) sensor or Mass Air Flow (MAF) sensor value. The EMS uses this information to calculate fuel delivery and ignition timing requirements.
Engine Management Systems on vehicles equipped with an electronic transmission utilize the TPS sensor in combination with MAP and MAF sensor values to determine shift schedules and torque converter clutch application.
Some vehicles will also incorporate a throttle switch. The throttle switch is used to notify the EMS when the throttle is either at wide-open throttle or at idle.
A faulty throttle position sensor or switch due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit can cause the following symptoms: