Automotive Keys are used to open and start vehicles. The mechanical blade has remained a feature for many years as a first line of security for the vehicle and in modern cars as a back up if the central locking remote control fails. Blade designs are usually symmetrical and can have cuts on both edges (cylinder style), on both faces (laser style) or on 4 sides (cruciform). Each type requires a specific type of key cutting machine which clamps the blade in place and will either copy an existing key or cut a new key to the vehicle key code which matches the locks.
Advances in technology has resulted in the use of Transponder Immobiliser Systems, which have increased considerably in complexity as time has gone by. Basically this system involves the inclusion of a small transponder chip placed inside the ignition key. See the information on Transponders below.
The inclusion of Transponders in vehicle keys means that whenever additional/replacement keys are required, they must be programmed into the vehicle using specialist diagnostic equipment.
One of the critical factors when programming additional/replacement keys, is the key itself, which in many cases must be original.
A Transponder is short for: transmitter + responder. The word was invented around 1944. In basic terms a transponder is a miniaturised electronic chip that has what is called Non-Volatile Memory. Non-Volatile Memory is the type of memory that does not need constant energy for retention. Along with that electronic chip is a set of windings, very fine wire coiled around a tube. These windings look similar to the windings you would find in an electric motor.
There are two basic types of Transponders. The first are the Electric Coupled Transponder Systems. Electric Coupled Transponder Systems are not limited to small areas for transmission but can transmit messages or signals for different ranges of distance including several inches to miles, as used in satellites and airplanes. These systems require large amounts of constant electricity to operate.
The second type is the one that automobile manufacturers use, which are called Magnetic Coupled Transponder systems. Magnetic Coupled Transponder systems are passive in nature. This means they do not require constant electricity and thus, do not need a power source of their own. They operate in the frequency range area of 125 kHz. Since Magnetic Coupled Transponders do not have their own power source they are very limited to range of communication and generally operate in the range of 1 cm to 15 cm. Since this is a radio frequency it can penetrate materials that would make the transponder not directly visible, such as the plastic or rubber in the bow of a key.
The process of key identification is similar in most Automotive Transponder Systems. Once a key is inserted into the ignition lock and turned to one of the ‘on’ or ‘run’ positions, the induction coil that is mounted around the ignition lock sends out an electromagnetic field of energy. The windings in the transponder chip absorb that energy and power the electronic chip to emit a signal. The signal is usually an alphanumeric set of digits (hexadecimal) which is considered the Identification Code. The induction coil reads the signal. If the signal is recognised as being already in the computer’s memory the signal is accepted and other electronic components in the vehicle are set into motion to allow the starting of the vehicle or the continuation of the engine running.
- Induction coil sends out an electromagnetic energy field.
- Windings on the transponder absorb the energy & power the electronic circuit to send out a signal.
- The signal is a digital code sent to the security module.
- If the code is recognised by the security module it will allow the vehicle to start.
- Since 1994 most vehicle manufacturers have fitted various types of alarms/immobilisers in response to Government reports on increased car theft
- Technology has driven improvements in vehicle security systems
- Although good for crime statistics, these advances pose problems for the vehicle owners and aftermarket diagnostics
- Transponder technology has developed from fixed code to rolling code
- All work associated with transponders/immobilisers was retained in the VM dealers
- Advanced Diagnostics was the first company to develop a specific tool for Key Programming – AD100
- Advanced Keys were set up to support the Advanced Diagnostics’ equipment as a route to genuine parts
Transponder System Types
- Fixed Code The transponder is energised and sends a fixed code to the security module.
- Rolling Code The transponder is energised and sends a code to the security module. The next time the transponder sends a code it will have rolled to the next code, which the vehicle knows because it has the calculation in memory. Later rolling code systems use more information, such as vehicle identification number (VIN) data to further protect the transponder.
- Texas Instruments
CENTRAL LOCKING REMOTE CONTROLS
Central locking remote controls come in all shapes and sizes with varying numbers of buttons which control not just the central locking system, but also the lights, windows, boot/tailgate opening, individual door opening, panic button and other alarm functions. They can be included as part of the key or be a separate unit.
These remote controls operate on either infra red or radio frequency signals, the latter being the most popular on modern vehicles. The radio frequency used is 433 MHz for Europe and 315 MHz for USA, South America and Japan with other territories having a mixture of the two depending on where cars are built or imported from.
Keyless entry (or proximity) versions are now becoming more popular. This is where the buttons on the remote control do not need to be depressed to open the vehicle, but when the remote control is within a set distance of the vehicle, the central locking will operate and as long as the remote control is within the vehicle, a button can be used to start the engine.
The programming of central locking remote controls is either a manual procedure unique to the vehicle or system used (which is normally outlined in the owner’s handbook), or a diagnostic procedure which involves plugging key programming equipment into the vehicle’s diagnostic socket.
Important Note Although many remote controls look similar or even identical to each other, the correct one that is specified for the vehicle should always be used. There are many differences in the operation of the various systems, so to save time it is important to check that the correct part is being used.