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 trunk lid/tailgate
• 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 (RKE). 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 same hand that is used to turn the starter, the ignition key may not be identified correctly. This will display an error message in the Driver Information Module (DIM). The vehicle will not start either. The vehicle will start, however, if the starter is turned to 0 and a new starting attempt is made. The fault will not generate a diagnostic trouble code. This fault is rare.
2. If a button on the remote control is pressed when the Keyless Vehicle Module (KVM) attempts to read the identity of the ignition key, the reading will fail. This is because the ignition key cannot not transmit and receive data at the same time (pressing a button on the remote control will mean the ignition key is engaged in transmitting a "normal" remote control command). This fault could occur if the key is kept in a pocket or bag and a button is pressed by mistake.
3. Due to increased external radiation, for example from TV/radio transmitters and mobile telephones, the signal from the remote control can on rare occasions be jammed. This is a rare fault but it can occur, especially in particular places where different external signals can impair transmitting and reception conditions. This is not only associated with keyless systems but can also affect different types of wireless communication.