Products suited to this guided test*
  • TA330-KeylessEntryDetector

    Keyless entry carrier signal detector

  • *At Pico we are always looking to improve our products. The tool used in this guided test may have been superseded and the product above is our latest version used to diagnose the fault documented in this case study.

Keyless entry

The purpose of this test is to evaluate the keyless entry and keyless starting system operation using a Keyless entry carrier signal detector.

How to perform the test

View connection guidance notes.

  1. Ensure the vehicle is locked and that the key is outside the detection zones.
  2. Connect the Keyless entry carrier signal detector to PicoScope Channel A.
  3. Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
  4. Start the scope to see live data.
  5. Hold the Keyless entry carrier signal detector around 300 mm from the door handle. Move it closer or further away until a signal is detected.
  6. Introduce a known good vehicle key to observe how the detected signal changes upon recognition of the key's presence.
  7. With your waveforms on screen stop the scope.
  8. Use the Waveform Buffer, Zoom and Measurements tools to examine your waveforms.

Example waveform

No key in the detection zones.

Key in a detection zone.

Waveform notes

These known good waveforms have the following characteristics:

  • Without a functioning key within the detection zones, the keyless entry system emits regular pulses at 0.25 s intervals.
  • The pulse amplitudes depend on the proximity of the Keyless entry carrier signal detector to a system antenna. The closer it is the higher the pulse amplitudes.
  • With a functioning key in a detection zone, the regular 0.25 s interval pulsations disappear and are replaced by much less frequent but slightly longer bursts of system activity.

Waveform Library

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select Keyless entry antennae.

Further guidance

Keyless entry systems are given many alternative names but they are commonly referred to as smart entry, smart start or Passive Keyless Entry (PKE) systems.

When the vehicle is locked the system uses antennae to periodically output a low frequency (LF) radio wave signal pulse. The pulses will trigger a response in a functioning key if it is within range. If the keyless entry system detects a response from a key it will deactivate the LF radio wave signal pulsations. Multiple antennae will be placed around the vehicle to ensure that the system has good coverage. The detection area formed by the front door antenna and outside luggage antenna is approximately 0.7 to 1.0 m (2.30 to 3.28 ft.) from the outside handle of the front door and rear bumper.

Many systems will extend the intervals between the LF radio wave signal pulses if a key has not been detected within a specified time. For example, the pulse intervals may extend from 250 ms to 750 ms if no key has been detected within a period of 5 days. If there is no activity within 14 days, then the system may be deactivated altogether so as to avoid draining the vehicle battery.


Vehicle entry issues may be remedied by one or more of the following checks and actions:

  • Key battery - check the key fob battery.
  • Vehicle battery - check the vehicle battery’s states of health and charge.
  • Bodywork - check that there is no excessive or additional door or door handle paintwork.
  • Environment - check there are no radio waves sources, such as TV towers, power plants, broadcast stations or gas stations, in the vicinity of the vehicle when the problem occurs.
  • Mobile phones - check that mobile phones are not carried near or with the key.
  • System status - check that the system has not been disabled (some manufacturers provide customers with this option).
  • Key programming - check that the key has been programmed to the vehicle.

The Keyless entry carrier signal detector provides a non-intrusive indication of the electrical key antenna and electrical key oscillator activity. However, there may be additional diagnosis methods at your disposal: most manufacturers will utilize self-diagnosis procedures or allow for controller interrogation with a scan tool which can support any errors found with keyless entry and keyless start.

For vehicles without self-diagnosis facilities, or where the relevant scan tool/software cannot gain controller access, the Keyless entry carrier signal detector provides essential information on whether the system is operating as it should or if there are dead zones where a key oscillator is no longer working and the key cannot be detected.

Further uses

The Keyless entry carrier signal detector can be used to detect keyless start systems: most vehicles equipped with a keyless entry system will also have a keyless start system. Electrical key oscillators are positioned at various points throughout the vehicle to help detect when the key is in the car.

Electrical key oscillators can be pinpointed with the Keyless entry carrier signal detector lead by “sniffing” out the emitted radio waves. As with the electrical key antennas, the closer you are to the source, the greater the output. This process can also be used to check the start/stop button function.

Note that the keyless start/stop system may time out around 30 seconds after a door has been opened. It can only be started again when the door has been closed or opened, or by operating the courtesy light switch.


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.

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Guided test: Keyless entry