Throttle position potentiometer

The purpose of this test is to evaluate the correct operation of the throttle potentiometer based on the output voltage and response time in relation to the throttle position.

Connection guidance

Connection for diagnostic work will vary dependent on application.

Technicians should whenever possible gain access to the test circuit without damage to seals and insulation. If this is not possible then make sure appropriate repairs are completed.

General connection advice:

PicoScope offers a range of options within the test kits.

Dependent on difficulty of access, choose from,

  1. Breakout leads.
  2. Back-pinning probes.

Testing sensors and actuators (to include relevant circuit/connectors):

  • When testing a sensor, it is desirable to gain access at the control module.
  • When testing an actuator, it is desirable to gain access at the actuator.

How to perform the test

  1. Use the vehicle wiring diagram to identify the signal circuit.
  2. Connect PicoScope Channel A to the vehicle.
  3. Start the engine and allow it to idle.
  4. Minimise the help page and with the example waveform on your screen PicoScope has already selected suitable scales for you to capture a waveform.
  5. Select GO or press the space bar to see live data.
  6. Carry out a WOT test.
  7. With your live waveform on screen select STOP or press the space bar to stop your capture.
  8. Turn off the engine.
  9. Use the WAVEFORM BUFFER and ZOOM tools to examine your waveform.

Example waveform

Waveform notes

This sensor or potentiometer is able to indicate to the Electronic Control Module (ECM) the exact amount of throttle opening due to its linear output.
The majority of modern management systems will employ this particular sensor, and is located on the throttle butterfly spindle. This is a 3 wire device having a 5 volt supply, an earth connection and a variable output from the centre pin. As the output is critical to the vehicle's performance, any 'blind spots' within the internal carbon track's swept area, will cause 'flat spots' and 'hesitations'. This lack of continuity can be seen on an oscilloscope and will enable the operator to plot the output voltage over its operational range, showing any faulty areas.

A good throttle potentiometer should show a small voltage at the throttle closed position, gradually rising in voltage as the throttle is opened and returning back to its initial voltage as the throttle is shut. Although many throttle position sensor voltages will be manufacturer specific, many are non-adjustable and the voltage will be in the region of 0.5 to 1.0 volts at idle rising to 4.0 volts (or more) with a fully opened throttle. For the full operational range, a time scale around 2 seconds is used.

The picture should be clean with no voltage 'drop out' at any particular point, as this small discrepancy will be sufficient to cause a 'flat spot' under initial acceleration.

Waveform Library

The Waveform Library has 123 examples for Throttle Position Sensor.

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

Example Potentiometer

Further guidance

This sensor or potentiometer is able to indicate to the ECM the exact amount of throttle opening. A throttle switch is unable to give precise increments of opening; however, a throttle potentiometer will be able to give exact openings due to its linear output. The majority of modern management systems will employ this particular sensor, and like the throttle position switch, it is also located on the throttle butterfly spindle.
This is also a 3 wire device having a 5 volt supply, an earth connection and a variable output from the centre pin.

As the output is critical to the vehicle's performance, any 'blind spots' within the internal carbon track's swept area, will cause flat spots and hesitations. This lack of continuity can be seen on a multimeter, however the use of an oscilloscope will enable the operator to plot the output voltage over its operational range, showing any faulty areas. A good throttle potentiometer with no faults should provide the waveform indicated above.

Selection of generic DTC's

Throttle position.

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

    £48.00

  • Flexible Back-pinning Probe

    £4.25

  • PicoScope Battery Clip

    £2.75

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Guided test: Throttle Potentiometer