Remote Control/Passive Key

Fig 1: Identifying Remote Control

Courtesy of VOLVO CARS CORPORATION

The remote control is identical in appearance in all markets. The differences are internal, depending on whether it has functionality for keyless entry or not. All remote controls also contain a key blade. The key blade is normally retracted inside the remote control. The blade is used as a standby option to open the vehicle should there be a fault in the system.

The buttons on the remote control are: 

• Lock  - to lock the vehicle
• Unlock  - to unlock the vehicle
• A button to unlock the boot lid/luggage compartment lid
• A button to activate the vehicle lighting for 30 seconds
• A button to manually trigger the alarm if an alarm is installed.

Internally, the remote control consists of three sections: 

• Transponder
• Circuit for remote control
• Circuit for keyless functionality.

The transponder is used so that the immobilizer system can identify the key when it is inserted in the ignition switch. The transponder contains a unique code. The central electronic module (CEM) must be programmed with the transponder code before the vehicle can be started.

The circuit for remote control is used to lock and unlock the central locking and to activate the above functions. The circuits in the remote control which control the remote control functionality are coded. These codes must be programmed into the keyless vehicle module (KVM) for communication to work.

The circuit for keyless functionality is used for: 

• Unlocking
• Locking
• Passive starting

The circuits in the remote control which control the function for the keyless entry system are coded. The keyless vehicle module (KVM) must learn these codes for communication to function.

The remote control is powered by an internal button battery. The battery is used each time a key needs to communicate with the system via the remote control or keyless entry function. The battery is not used during communication with the key transponder when the key is in the ignition switch. The battery must be replaced at regular intervals depending on how often the remote control is used. The remote control contains an internal voltmeter that measures the voltage of the internal battery. If the battery voltage is low, this information is transmitted in the messages transmitted to the 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, such cases, displays a message that the voltage for the remote control is low.

1. If the ignition key is held in the hand that is used to turn the starter switch, the ignition key identification can fail. This results in a message being shown in the driver information module (DIM). The vehicle will not start either. However, the vehicle will start if the starter switch is turned to position 0 and another start attempt made. The fault does not generate any diagnostic trouble codes (DTCs). The fault is rare.
2. If a button on the remote control is pressed when the keyless vehicle module (KVM) attempts to read out the identity of the ignition key, reading off will fail. This means that the ignition key cannot transmit and receive data at the same time (when a button is pressed on the remote control, the ignition key is busy sending "normal" remote control commands). This fault may occur if the key is in a pocket or bag and a button has been pressed by mistake.
3. Due to increased ambient radiation, for example, from TV/radio transmitters and mobile phones, the signal from the remote control can, in some cases, be interrupted. This is rare but can happen. 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.
4. If the remote control is stored together with a mobile phone in a pocket or purse, it can happen that the mobile phone's signal blocks the remote control's signal to the vehicle. If the remote control's signal to the vehicle is blocked and at the same time the customer tries to open the door by pulling the handle, the feature will not work. The same applies if the remote control's signal is blocked and at the same time the customer tries to unlock the vehicle by pressing the button on the door handle. If this symptom occurs, then no components are to be replaced. Instead, instruct the customer not to store the remote control together with a mobile phone. In order to achieve a flawless function, the remote control and mobile phone must be kept at least 10-15 cm apart.