Chassis / TPMS

TIRE PRESSURE MONITORING SENSOR

Measures tire pressure and temperature and transmits wheel identification wirelessly.

SENSOR GUIDE29/86

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 01CONSTRUCTION VARIANT

Analog voltage

Confirm wiring, pin count and service information before testing.

Usually a three-wire reference, ground and proportional signal circuit.

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

+ Verify reference and ground under load; back-probe the signal through the complete operating range.

+ Verify the specified supply, ground, bias or termination before judging the signal.

+ Repeat the test through the complete operating range.

EXPECTED

✓ Output matches this construction type

✓ Stable levels and repeatable response

✓ Agreement with related scan data

COMMON FAULTS

— Incorrect test method for the sensor type

— Supply, ground or signal-circuit fault

— Installation, target or calibration concern

TYPE 02CONSTRUCTION VARIANT

SENT / PWM / frequency

Confirm wiring, pin count and service information before testing.

The measured value is encoded digitally on a dedicated signal wire.

Reading the signal

Good waveform

Check the correct physical interface and decode the transmitted data. Valid frames, expected update timing and measurements that agree with the real input support normal operation. Pulse shape alone does not establish measurement accuracy.

Faulty waveform

Corrupted or missing frames, unexpected pauses, invalid status bits or implausible decoded values can indicate a fault. Verify supply, ground and the applicable bus before replacing the sensor; do not apply CAN waveform expectations to LIN, SENT or another interface.

TYPE-SPECIFIC TESTS

+ Scope pulse timing or duty cycle with the correct pull-up and decode it only with compatible equipment.

+ Verify the specified supply, ground, bias or termination before judging the signal.

+ Repeat the test through the complete operating range.

EXPECTED

✓ Output matches this construction type

✓ Stable levels and repeatable response

✓ Agreement with related scan data

COMMON FAULTS

— Incorrect test method for the sensor type

— Supply, ground or signal-circuit fault

— Installation, target or calibration concern

TYPE 03CONSTRUCTION VARIANT

Networked smart sensor

Confirm wiring, pin count and service information before testing.

Internal electronics report the value through LIN, CAN or a local module.

Reading the signal

Good waveform

Check the correct physical interface and decode the transmitted data. Valid frames, expected update timing and measurements that agree with the real input support normal operation. Pulse shape alone does not establish measurement accuracy.

Faulty waveform

Corrupted or missing frames, unexpected pauses, invalid status bits or implausible decoded values can indicate a fault. Verify supply, ground and the applicable bus before replacing the sensor; do not apply CAN waveform expectations to LIN, SENT or another interface.

TYPE-SPECIFIC TESTS

+ Test powers, grounds and network integrity; compare scan data with an independent physical measurement.

+ Verify the specified supply, ground, bias or termination before judging the signal.

+ Repeat the test through the complete operating range.

EXPECTED

✓ Output matches this construction type

✓ Stable levels and repeatable response

✓ Agreement with related scan data

COMMON FAULTS

— Incorrect test method for the sensor type

— Supply, ground or signal-circuit fault

— Installation, target or calibration concern

Correct theory and operation

HOW IT
WORKS.

Understand the sensing method, circuit and controller strategy before interpreting data or replacing the component.

01

Measured condition

Measures tire pressure and temperature and transmits wheel identification wirelessly.

02

Signal type

Wireless pressure and temperature data. A battery-powered wheel sensor measures pressure and temperature, then broadcasts its identity and readings to a receiver.

03

Controller use

The receiving controller checks range, rationality and rate of change against related inputs before setting a fault or substituting a value.

04

Installation matters

Mounting, target condition, air gap, contamination, temperature, shielding or calibration may affect the result even when the circuit is intact.

Common mistakes

AVOID THE
FALSE CLUE.

COMPLETE TEST SEQUENCE

  1. Confirm sensor IDs and receiver communication with a TPMS tool.
  2. Compare reported pressure with an accurate mechanical gauge.
  3. Check wheel location, frequency compatibility and relearn status.
  4. Inspect for sensor damage during tire service.
  5. Repeat the original operating condition and confirm the repair.
DO NOT CONDEMN THE SENSOR

Prove its supply, ground, signal path, physical input and calibration before replacement. Vehicle-specific specifications always win.

SENSOR LIBRARYReturn to all sensors→

Diagnostic details

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.

Direct Radio TPMS Sensor

A wheel-mounted pressure sensor transmits pressure, identification and often temperature wirelessly.

Operating principle

  • A wheel-mounted pressure sensor transmits pressure, identification and often temperature wirelessly.

Circuit identification

Application-specific; see wiring below

Wiring

  • An internal battery or other specified power arrangement; the wheel sensor is not a generic wired MAP sensor.

Expected readings

  • Reported pressure should agree with a calibrated gauge and the correct wheel ID.

Multimeter testing

  • Use a compatible TPMS activation tool to read each sensor, compare gauge pressure and check relearn requirements.

Oscilloscope setup

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

Oscilloscope testing

  • Use a compatible TPMS activation tool to read each sensor, compare gauge pressure and check relearn requirements.
  • Indirect TPMS estimates tire behavior from wheel-speed data and has no pressure sensor in each tire. Do not back-probe the sealed wheel sensor.

Waveform interpretation

Reported pressure should agree with a calibrated gauge and the correct wheel ID. 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

  • Indirect TPMS estimates tire behavior from wheel-speed data and has no pressure sensor in each tire. Do not back-probe the sealed wheel sensor.
  • Construction, output format and number of redundant channels are separate attributes.