TPSSensor

Throttle Position Sensor (TPS)

Group: Air and fuel

The TPS reports how far the throttle plate is open. The computer uses it for acceleration enrichment, fuel cut-off on deceleration, idle control and automatic transmission shifts.

Contents

What does the TPS sensor do?

It is a potentiometer (or a contactless Hall effect sensor on modern models) attached to the throttle shaft. It delivers a low voltage with the throttle closed and a high voltage at wide open throttle. Electronic throttle bodies (drive-by-wire) have two TPS tracks that monitor each other: if they disagree, the computer limits power (limp mode).

Where is it located?

On the throttle body, at the end of the throttle shaft.

Signal type and reference values

  • 3 wires per track: 5 V, ground and signal.
  • Throttle closed: roughly 0.4 to 0.9 V.
  • Wide open throttle: 4.0 to 4.8 V.
  • On electronic systems the two tracks usually run in opposite directions or with different slopes; their sum or ratio must stay constant.

Values are a guide only: always check the manufacturer's data for your engine.

Symptoms of a bad TPS sensor

  • Bucking or a flat spot when you press the accelerator.
  • High or unstable idle.
  • Harsh or late shifts on an automatic transmission.
  • Limp mode: the engine will not rev past 2,000 to 3,000 RPM.
  • Codes P0120 to P0124, or P2135 on electronic throttles.

How to test the TPS sensor step by step

  1. Ignition on, engine off: check for 5 V supply and ground at the connector.
  2. Open the throttle slowly (by hand, or with the pedal on electronic systems) and watch the voltage or percentage on the scan tool: it should rise continuously, without jumps or dropouts.
  3. Wiggle the connector and wiring while you watch the reading to catch intermittent contacts.
  4. Clean the throttle body: carbon buildup stops the plate from closing fully.
  5. After cleaning or replacing the throttle body, run the throttle position relearn with a scan tool or the manufacturer's procedure.

Trouble codes related to the TPS sensor

Frequently asked questions about the TPS sensor

Does the TPS need to be calibrated?
On older units with adjustment screws, yes: the closed-throttle voltage must be set to the value in the manual. Electronic units are not adjusted: you run a relearn with the scan tool.
Are the TPS and the pedal sensor the same thing?
No. The TPS measures the throttle plate. The APP sensor measures the accelerator pedal. On electronic systems the computer compares both.

Updated September 25, 2026. Values are a guide only: always confirm them in the service manual for your engine.

Other sensors