Remote Key
The remote key is used to activate functions in the system remotely. The remote key has buttons for activating the following functions:
- unlocking and locking the side doors
- unlocking the tailgate
- activating the local lighting
- activating alarm functions.
The remote key, regarding internal design, consists of:
- transponder
- function for remote control.
The transponder is a communication circuit in the head of the key. The transponder has a unique identification code which connects the remote key to the vehicle. The transponder is coded. This code must be learned by the central electronic module (CEM) before the remote key can be used to start the vehicle. Once the transponder has been programmed for one vehicle, it cannot be programmed for another.
The remote key has a built-in communication circuit and a memory. A coded signal is sent when a button on the remote key is pressed. This signal is received by the Remote Receiver Module (RRX) receiver and forwarded to the central electronic module (CEM). For the remote key to work with the system, a unique code in the remote key must be learned by the central electronic module (CEM). This takes place during installation at the factory.
The remote key has a key blade which is normally retracted inside the remote key. The key blade can be used in emergency situations to unlock the driver's door. This does not disarm alarm functions however, so should only be used as a last resort to open the car.
The remote key has an integrated battery which is used when commands are sent to the system. This battery must be replaced regularly. The remote key contains an internal voltmeter that measures the voltage on the internal battery. If the battery voltage becomes too low, information about this is transmitted in the messages to the Remote Receiver Module (RRX). The central electronic module (CEM) receives this information and transmits a message via the CAN network to the Driver information module (DIM), which shows a message that the voltage for the remote key battery is too low. Reduced remote key range is also an indication that the battery charge is low.
In certain cases malfunctions may occur in the system when communication between the Remote Receiver Module (RRX) and the remote key is interrupted for different reasons. Malfunctions are not due to any electrical faults and do not generate any diagnostic trouble codes (DTCs). Due to increased ambient radiation, for example, from TV/radio transmitters and mobile phones and meters with remote reading, the signal from the remote key can, in some cases, be interrupted. In many cases this occurs in particular locations, where different outside signals make transmission and reception conditions unfavorable. This affects not only central locking systems but all types of wireless communication.