Remote Key

Fig 1: Identifying Remote Key

Courtesy of VOLVO CARS CORPORATION

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
• status check of lock status and activation of heart beat sensor.

The remote key, regarding internal design, consists of three sections: 

• transponder
• function for remote control
• function for the keyless entry system, if applicable.

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 a remote keyless entry (TRX) receiver and is forwarded on to the keyless vehicle module (KVM). For the remote key to work with the system, a unique code in the remote key must be learnt by the keyless vehicle module (KVM). This takes place during installation at the factory.

The keyless entry system is used for: 

• unlocking
• locking
• passive starting
• passive key warning.

Normally two remote keys are programmed for the vehicle on delivery. Additional remote keys can be added afterwards.

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 remote keyless entry (TRX). The Keyless vehicle module (KVM) 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.

1. If a button on the remote key is depressed when the keyless vehicle module (KVM) attempts to read the identity of the remote key, read off will fail. This means that the remote key cannot transmit and receive data at the same time (when a button is pressed on the remote key, the remote key is busy sending "normal" remote control commands). This fault may occur if the remote key is in a pocket or bag and a button has been pressed by mistake.
2. 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 certain locations, where different outside signals make transmission and reception conditions unfavorable. This affects not only keyless vehicle systems but all types of wireless communication.