Throttle Position Sensor: Operation

The TPS is a 3-wire variable resistor that provides the Powertrain Control Module (PCM) with an input signal (voltage) that represents the throttle blade position of the throttle body. The sensor is connected to the throttle blade shaft. As the position of the throttle blade changes, the resistance (output voltage) of the TPS changes.

The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. The PCM receives an input signal voltage from the TPS. This will vary in an approximate range of from .26 volts at minimum throttle opening (idle), to 4.49 volts at wide open throttle. Along with inputs from other sensors, the PCM uses the TPS input to determine current engine operating conditions. In response to engine operating conditions, the PCM will adjust fuel injector pulse width and ignition timing.

The PCM needs to identify the actions and position of the throttle blade at all times. This information is needed to assist in performing the following calculations:

• Ignition timing advance
• Fuel injection pulse-width
• Idle (learned value or minimum TPS)
• Off-idle (0.06 volt)
• Wide Open Throttle (WOT) open loop (2.608 volts above learned idle voltage)
• Deceleration fuel lean out
• Fuel cutoff during cranking at WOT (2.608 volts above learned idle voltage)
• A/C WOT cutoff (certain automatic transmissions only)