Disassembly of the car's keyless system: the internal circuit principle of the remote control

The keyless entry and start system is referred to as the PEPS (Passive Entry Passive Start) system, which is composed of the on-board computer receiving and sending circuits, the internal circuits of the smart key, etc. When the key is within the effective range, generally within 3M, press the door button or the remote unlocking button, the wireless system exchanges data with the smart key, the authentication is passed, and an interrupt signal is sent to wake up the ECU, the door lock is opened, enter the car and press the one-button start to start the starter. The whole process does not require the use of the key, and the ECU periodically polls whether the key is within the effective range. Different models have different detection methods.

With the widespread use of technology in car design, low-end cars are also adopting this technology, and now the way to drive a car is becoming more and more convenient. In the past, mechanical keys were used to unlock the vehicle, and later button-type remote control keys appeared. Now the most common way to enter a car is the keyless system.

The working principle of automobile PEPS is as follows: the PEPS system uses radio frequency communication between the ECU and the key. The low frequency of 125 kHz and the high frequency of 433M signals transmit the unique key access code between the remote control key and the vehicle. When you walk near the car with the car key, the car will send and send a signal to the low frequency signal. The key receives and responds. Some car door locks open automatically. You can just pull the car door directly, and some cars need to press the door handle button. Only when the exchanged code matches the expected value and the remote control key is within the effective distance of the unlocked vehicle, the vehicle can be unlocked. There are multiple antennas on the car to determine the strength of the signal sent by the key and whether the key is inside or outside the car. If the key is close but still outside the car, the signal strength is not enough, the car will not unlock, and the horn will sound an alarm. When locking and unlocking the car remotely, high frequency 433M remote communication is used to send unlock and lock signals. The PEPS system can be a trigger system or a polling system. If it is a trigger system, the driver starts the car entry process by touching the door handle. If it is a polling system, the car entry system will continue to scan and search for the key within a nearby distance. The PEPS system provides convenience and comfort, and more importantly, greatly improves safety.