Throttle position sensor (potentiometer) - voltage

The purpose of this test is to examine the operation of a throttle potentiometer based on quality of output and response time in relation to throttle position.

How to perform the test

View connection guidance notes.

  1. Use manufacturer's data to identify the position sensor output circuit.
  2. Connect PicoScope Channel A to the sensor output circuit.
  3. Turn ignition on engine off.
  4. Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
  5. Start the scope to see live data.
  6. Carefully and slowly fully open and close the throttle.
  7. With your waveform on screen stop the scope.
  8. Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.

Example waveform

Waveform notes

This known good waveform has the following characteristics:

  • A steady unbroken voltage output signal with a value of 0.7 V at engine idle.
  • As the throttle begins to open, at just after 0.5 s the signal has an immediate steady unbroken rise to 3.6 V with no irregularities.
  • The 3.6 V signal is maintained for around 0.5 s before a gradual unbroken descent back to the 0.7 V idle value.

Waveform Library

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select Throttle Position Sensor TPS.

Further guidance

Throttle potentiometers are generally carbon track type units mounted directly onto the throttle butterfly spindle. They are a three-wire device with a reference 5 V supply, output signal and earth terminals.

Some manufacturers combine the potentiometer with the throttle actuator motor. Whether combined, or a separate component the potentiometer will have the same function.

The primary function of the unit is to provide voltage signals to the Engine Control Module (ECM) reporting the position of the throttle valve.

Different manufacturers will use slightly different check parameters but generally a signal exceeding 4.5 V or a signal lower than 0.2 V will be outside of parameters and register as a sensor fault.

Faulty Throttle Potentiometer – Symptoms

  • Malfunction Indicator Lamp (MIL) on.
  • Hesitation in throttle response.
  • Poor/erratic starting.
  • Engine jolts or splutters.
  • Increased fuel consumption with associated increase in emissions.

Faulty Throttle Potentiometer – Causes

  • Mechanical damage caused by heat and vibration.
  • Internal short circuits caused by fluid contamination and humidity.
  • Contact and external circuit damage.
  • Frictional wear of moving parts.

Diagnostic trouble codes

Selection of component-related Diagnostic Trouble Codes (DTCs):

P0120 - TP System Performance

P0121 - TP Sensor Circuit Insufficient Activity

P0122 - Throttle Position (TP) Sensor Circuit Low Voltage

P0123 - Throttle Position (TP) Sensor Circuit High Voltage

P0124 - Throttle Position Sensor 1 Circuit Intermittent

P0221 - APP (Throttle Position) Sensor 2 Circuit Performance

P0222 - APP (Throttle Position) Sensor 2 Circuit Low Voltage

P0223 - APP (Throttle Position) Sensor 2 Circuit High Voltage

P0224 - Throttle Position Sensor 2 Intermittent

P0229 - Throttle Position Sensor 3 Intermittent

P1120 - Throttle Position (TP) Sensor 1 Circuit

P1121 - Throttle Position (TP) Sensor Circuit Intermittent High Voltage

P1122 - Throttle Position (TP) Sensor Circuit Intermittent Low Voltage

P1125 - Accelerator Pedal Position (APP) System

P1219 - Throttle Position Sensor Reference Voltage

P1220 - Throttle Position (TP) Sensor 2 Circuit

P1515 - Electronic Throttle System Throttle Position

P1516 - Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance

P1517 - Electronic Throttle Module

P1518 - Electronic Throttle Module to PCM Communication

P1519 - Throttle Actuator Control (TAC) Module Internal Circuit

P1523 - Throttle Closed Position Performance

P1524 - Throttle Closed Position Performance

P1525 - Throttle Body Service Required

P1526 - Minimum Throttle Position Not Learned

P1890 - Throttle Position Signal Input

P1891 - Throttle Position Sensor PWM Signal Low

P1892 - Throttle Position Sensor PWM Signal High

P2120 - Accelerator Pedal Position (APP) Sensor 1 Circuit

P2121 - Accelerator Pedal Position (APP) Sensor 1 Performance

P2122 - Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage

P2123 - Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage

P2125 - Accelerator Pedal Position (APP) Sensor 2 Circuit

P2127 - Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage

P2128 - Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage

P2135 - Throttle Position (TP) Sensor 1-2 Correlation

P2138 - Accelerator Pedal Position (APP) Sensor 1-2 Correlation

P2176 - Minimum Throttle Position Not Learned

B2105 Throttle Position Input Out of Range Low

B2106 Throttle Position Input Out of Range High

GT029-3

Disclaimer
This help topic is subject to changes without notification. The information within is carefully checked and considered to be correct. This information is an example of our investigations and findings and is not a definitive procedure. Pico Technology accepts no responsibility for inaccuracies. Each vehicle may be different and require unique test settings.

Suitable accessories

  • Premium 6-way breakout lead set

    £269.00

  • Back-pinning Probe Set

    £40.00

  • Flexible Back-pinning Probe

    £3.00

  • PicoScope Battery Clip

    £2.75

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Guided test: Throttle position sensor (potentiometer) - voltage