A TPS, or Throttle Position Sensor, is a critical component of your car's engine management system. It's a sensor located on the throttle body that monitors the position of the throttle plate. When you press the gas pedal, the throttle plate opens to allow more air into the engine. The TPS sends a real-time voltage signal to the car's computer (the Engine Control Unit or ECU), telling it how far the throttle is open. The ECU uses this data, along with information from other sensors, to calculate the perfect amount of fuel to inject for optimal combustion, power, and efficiency.
A malfunctioning TPS can cause a range of drivability issues. Common symptoms include erratic idling, hesitation or stumbling during acceleration, unexpected stalling, and a noticeable drop in fuel economy. In modern vehicles, a faulty TPS will almost certainly trigger the Check Engine Light and store a diagnostic trouble code (DTC), such as P0120 or P0121.
Diagnosing a bad TPS typically involves using a multimeter or a scan tool to check if the sensor's voltage output changes smoothly as the throttle is opened and closed. Any sudden jumps, flat spots, or gaps in the voltage signal indicate a failing sensor. Replacement is generally straightforward but often requires recalibration of the ECU's learned values after installation.
| Common TPS-Related Diagnostic Trouble Codes (DTCs) | Description |
|---|
| P0120 | Throttle/Pedal Position Sensor/Switch "A" Circuit Malfunction |
| P0121 | Throttle/Pedal Position Sensor/Switch "A" Circuit Range/Performance Problem |
| P0122 | Throttle/Pedal Position Sensor/Switch "A" Circuit Low Input |
| P0123 | Throttle/Pedal Position Sensor/Switch "A" Circuit High Input |
| P0220 | Throttle/Pedal Position Sensor/Switch "B" Circuit Malfunction |
