Driver demand / TPS

THROTTLE POSITION SENSOR

A potentiometer or non-contact sensor reports throttle angle, commonly with two inverse signal tracks for plausibility checking.

FIELD GUIDE05/13

Identify the circuit first

ONE NAME.
DIFFERENT SIGNALS.

Pin count is a clue, not proof. Confirm the exact architecture before resistance testing, applying voltage or judging the waveform.

TYPE 01PASSIVE ELEMENT / ANALOG

Potentiometer TPS

5 V reference, low reference and wiper signal

A mechanical wiper creates a smooth voltage proportional to plate position.

Reading the signal

Good waveform

The measured signal changes consistently with the physical input and stays within the application-specific operating range. Under a steady input, it should remain stable apart from normal noise or control activity.

Faulty waveform

Dropouts, unexpected spikes, a signal pinned near a supply rail, or a biased reading can indicate a problem. Verify the real input, reference and loaded ground before blaming the sensor; a smooth signal can still be inaccurate.

TYPE-SPECIFIC TESTS

+ Sweep slowly key-on, engine-off.

+ Repeat through common cruise positions.

+ Watch for narrow dropouts a meter may miss.

EXPECTED

✓ Linear sweep

✓ Repeatable endpoints

✓ No discontinuities

COMMON FAULTS

— Worn track

— Open wiper

— Poor low reference

TYPE 02ACTIVE / DUAL ANALOG

Non-Contact Dual TPS

Shared supply/ground with two signal tracks

Magnetic or inductive electronics provide redundant signals, often inverse or ratio-related.

Reading the signal

Good waveform

Compare the measured signal with the specified input or command under the same operating conditions. Levels, timing and repeatability should match the installed design and a suitable verified reference. There is no universal waveform or scale for every version of this component.

Faulty waveform

An unexplained dropout, missing response, excessive noise or mismatch between command and feedback warrants further testing. First rule out a changed physical condition, incorrect probe reference, supply loss and an unsuitable scope setting; an unusual trace alone does not identify a failed component.

TYPE-SPECIFIC TESTS

+ Graph both tracks simultaneously.

+ Verify their specified sum or ratio across travel.

+ Check desired versus actual throttle under command.

EXPECTED

✓ Smooth correlated tracks

✓ Stable relationship

✓ No plausibility faults

COMMON FAULTS

— Track disagreement

— Shared-reference fault

— Internal electronics failure

Correct theory and operation

HOW IT
WORKS.

Understand the component, its circuit and the controller's strategy before interpreting the waveform or beginning disassembly.

01

Sensing principle

A potentiometer or non-contact sensor reports throttle angle, commonly with two inverse signal tracks for plausibility checking.

02

Circuit architecture

A contact potentiometer divides the reference voltage according to shaft position. Non-contact Hall or inductive designs sense a rotating magnetic target. Electronic throttles normally provide two tracks with deliberately different transfer functions.

03

Controller interpretation

The controller compares both tracks continuously, checks them against motor command and pedal demand, and limits throttle operation when correlation leaves its calibrated window. Absolute direction and ratio are application-specific.

04

Normal response

Smooth, linear sweep with no discontinuities. Dual tracks maintain the specified relationship. Closed and wide-open values remain repeatable.

05

System relationship

Judge the signal only under a defined operating condition. Verify its power, reference, ground, mechanical input and related scan data before deciding the sensing element is incorrect.

Common mistakes

AVOID THE
FALSE CLUE.

COMPLETE TEST SEQUENCE

  1. Key on, engine off; verify reference voltage and low reference.
  2. Open the throttle slowly from rest to full travel.
  3. Watch both tracks together where dual signals are used.
  4. Repeat slowly to expose worn spots or intermittent dropouts.
DO NOT CONDEMN A SENSOR

until its power, ground, signal circuit, mechanical target and related system inputs have been verified.

NEXT GUIDE / APPAccelerator Pedal Position Sensor→

Diagnostic details

Purpose

TPS information is used for electronic throttle control, engine load, acceleration strategy and plausibility monitoring.

Scan tool data

  • Commanded throttle
  • APP position
  • Throttle actuator command

Failure symptoms

  • Reduced power
  • Poor throttle response
  • High or unstable idle
  • Electronic throttle warning

Related DTCs

  • P0120 – TPS Circuit
  • P0121 – TPS Range/Performance
  • P0122 – TPS Circuit Low
  • P0123 – TPS Circuit High
  • P2135 – TPS Correlation

Diagnostic tips

  • Compare redundant throttle signals.
  • Compare commanded and actual throttle position.

Construction & type-specific testing

Identify the installed design before testing. Construction, signal format and redundant channels are separate attributes; use only the procedure for the actual component.

Potentiometer Position Sensor

A moving wiper changes the division of a reference voltage. Redundant tracks may share or have separate circuits.

Operating principle

  • A moving wiper changes the division of a reference voltage. Redundant tracks may share or have separate circuits.

Circuit identification

Application-specific; see wiring below

Wiring

  • Reference, low reference and wiper signals; count and track relationship vary.

Expected readings

  • Smooth repeatable travel without dropouts; redundant tracks maintain their specified relationship.

Multimeter testing

  • Graph all tracks during slow permitted travel. Check reference and low reference before diagnosing a worn track.

Oscilloscope setup

  • Identify the output interface and approved test points before connecting. Set the range, coupling and probes for that circuit.

Oscilloscope testing

  • Graph all tracks during slow permitted travel. Check reference and low reference before diagnosing a worn track.
  • Do not force an electronic throttle against its drive. Dual-track describes redundancy, not the sensing technology.

Waveform interpretation

Smooth repeatable travel without dropouts; redundant tracks maintain their specified relationship. No universal known-good waveform is specified for this design.

Common failures

  • Connection, supply or signal-path faults where applicable
  • Damage, installation error or loss of calibration appropriate to this design

Diagnostic tips

  • Do not force an electronic throttle against its drive. Dual-track describes redundancy, not the sensing technology.
  • Construction, output format and number of redundant channels are separate attributes.
Contactless Inductive Position Sensor

An excited coil system senses a conductive target without a sliding electrical contact.

Operating principle

  • An excited coil system senses a conductive target without a sliding electrical contact.

Circuit identification

Application-specific; see wiring below

Wiring

  • Powered electronics with application-specific analog or digital output.

Expected readings

  • Repeatable position data and correct redundant-channel correlation.

Multimeter testing

  • Verify power and ground, then compare channels throughout permitted travel. Decode the actual interface rather than testing internal coil resistance.

Oscilloscope setup

  • Identify the output interface and approved test points before connecting. Set the range, coupling and probes for that circuit.

Oscilloscope testing

  • Verify power and ground, then compare channels throughout permitted travel. Decode the actual interface rather than testing internal coil resistance.
  • An inductive target need not be a magnet. Confirm construction and interface from service information.

Waveform interpretation

Repeatable position data and correct redundant-channel correlation. No universal known-good waveform is specified for this design.

Common failures

  • Connection, supply or signal-path faults where applicable
  • Damage, installation error or loss of calibration appropriate to this design

Diagnostic tips

  • An inductive target need not be a magnet. Confirm construction and interface from service information.
  • Construction, output format and number of redundant channels are separate attributes.
Hall-Effect Position Sensor

A magnetic target changes the field measured by a powered Hall element.

Operating principle

  • A magnetic target changes the field measured by a powered Hall element.

Circuit identification

Application-specific; see wiring below

Wiring

  • Powered electronics; analog or digital channels depend on application.

Expected readings

  • Smooth position response with the specified channel relationship.

Multimeter testing

  • Check target alignment and graph redundant channels while moving through permitted travel.

Oscilloscope setup

  • Identify the output interface and approved test points before connecting. Set the range, coupling and probes for that circuit.

Oscilloscope testing

  • Check target alignment and graph redundant channels while moving through permitted travel.
  • Do not resistance-test powered sensor electronics or infer sensor type from wire count alone.

Waveform interpretation

Smooth position response with the specified channel relationship. No universal known-good waveform is specified for this design.

Common failures

  • Connection, supply or signal-path faults where applicable
  • Damage, installation error or loss of calibration appropriate to this design

Diagnostic tips

  • Do not resistance-test powered sensor electronics or infer sensor type from wire count alone.
  • Construction, output format and number of redundant channels are separate attributes.