What is TPS? (Throttle Position Sensor)
The TPS stands for Throttle Position Sensor. It is a sensor mounted on the throttle body that measures the opening angle of the throttle valve and sends this data to the ECU.
Function of TPS
- Detects throttle valve position (how much the driver presses the pedal).
- Sends signal to ECU for fuel injection control.
- Improves engine response and acceleration.
- Helps automatic transmission shifting in some vehicles.
- Supports idle and load calculations.
Location of TPS
- Mounted on the throttle body.
- Connected directly to the throttle shaft.
- Sometimes integrated into electronic throttle bodies.
Symptoms of a Faulty TPS
- Unstable or fluctuating RPM.
- Poor acceleration response.
- Increased fuel consumption.
- Engine hesitation or jerking.
- Check Engine Light ON.
- Incorrect automatic gear shifting.
OBD-II Trouble Codes Related to TPS
- P0120 – TPS circuit malfunction
- P0121 – Range/performance issue
- P0122 – Low input signal
- P0123 – High input signal
- P0124 – Intermittent signal
TPS Electrical Circuit
- 5V reference from ECU
- Ground wire
- Signal wire (variable voltage output)
The signal voltage increases smoothly as the throttle opens.
Voltage Range
- Closed throttle: 0.5V – 1.0V
- Wide open throttle (WOT): 4.0V – 4.8V
How to Test TPS
- Use a multimeter to measure signal voltage.
- Backprobe the signal wire while slowly opening the throttle.
- Voltage should increase smoothly without drops or spikes.
- Use OBD scanner to monitor live data (TPS %).
How to Replace TPS
- Disconnect the battery before work.
- Unplug the electrical connector.
- Remove mounting screws from throttle body.
- Install the new TPS and align correctly.
- Perform throttle relearn if required.
Important Notes
- TPS faults can look like fuel or ignition problems.
- Always confirm with live data and voltage testing before replacement.
- Sometimes the issue is wiring or throttle body, not the sensor itself.