The purpose of this test is to investigate the operation of a keyless entry system with the key both out of and in range of the vehicle antennas.
Repeat the test with the correct key in range to see the recognition waveform.
1. Low-frequency signal emitted by a functioning electrical key antenna at an approximate interval of 0.25 seconds.
2. Note how the voltage changes across the capture. This is due to the Keyless entry detector being moved closer to the door handle. The closer it gets the stronger the signal.
Changing the timebase to 1 ms/div and adding a trigger to Channel A on auto rising edge of approximately 2 V has made it easier to see a clearer waveform.
The output from a functioning electrical key antenna can be measured using the keyless entry detector, confirming activity of the antenna under test. Locking the vehicle and removing the key will trigger the LF signal to start searching for a key in the detection zone as in example waveform 1. Each antenna transmits the request signal received from the certification ECU and forms a key detection area to detect the presence of a key. 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.
When the key is brought into the detection area the signal from the electrical key antenna will change. This is visible in Example waveform 3. The voltage no longer spikes (depending on where the key detector is placed).
It is worth noting that most systems will extend the pulse time if the vehicle’s sensor cannot find a key in the detection zone or if the touchpad on the handle is pressed in a specified time. This usually happens after a period of 5 days, changing the signal from 25 ms to 75 ms. If the vehicle is left longer (approximately 14 days), with no activation or key detected, the system will deactivate to avoid draining the battery.
The keyless entry signal carrier detector can also be used to detect start systems. Most vehicles equipped with a smart entry 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 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 if the start/stop button is working correctly.
It is also important to note that the system times out at around 30 seconds of the door being opened. It can only be started again when the door has been closed or opened, or by operating the courtesy light switch.
While the Keyless entry detector can provide a non-intrusive indication of electrical key antenna and electrical key oscillator activity, 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 detector provides essential information on whether the system is operating as it should or if there are certain dead zones where a key oscillator is no longer working and the key cannot be detected.
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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