The EWS 2 System consists of the following components:
The transponder is a special transmitter/receiver in the key; it employs electronic transmission and reception circuitry (S/E module) to support communications with the EWS control unit. The transponder chip, which forms an integral part of the key, consists of this transmitter/receiver, a small coil aerial, and a read/write memory chip.
The transponder chip receives its electrical energy supply from the transmitter/receiver module via the coil aerial on the steering lock. There is thus no need for a battery in the key. In a process analogous to that of a transformer, power supply and data communications are conducted between the ring aerial (winding) in the ignition lock and the coil aerial integrated within the key unit. The maximum read/write data transfer range is 2 cm.
The transponder's memory contains:
Important!
Each individual key (with or without remote control) contains a transponder chip with its own key data, and is thus unique!
This coil consists of 75 individual windings and is installed on the ignition lock cylinder.
The transmitter/receiver electronics (S/E module) process and administer data communications with the transponder and communicate with the EWS control unit. Data transfer is via a single bilateral serial communications channel.
The S/E module is installed adjacent to the steering column. Power is supplied to the module from ignition key position 1 onward.
The EWS control unit serves as the interface linking the transmitter/receiver (S/E module), the engine control unit and the starter.
The EWS control unit's most important functions are:
Power supply is via Terminal 30.
The engine control unit (DME/DDE) has been designed to release the injection (Terminal 15) and the fuel supply only after having received a correct release signal from the EWS control unit.
This release signal is based on the I ndividual S erial Number (ISN) for the engine control unit.
The engine control unit (DME/DDE) must identify and recognize this release signal before it will activate the ignition signal (Terminal 15) and the fuel supply.
When the engine control unit is replaced, this means that an encoding device (DIS tester or MoDiC) must be used to enter the Individual Serial Number (ISN) for the new engine control unit (DME/DDE) into the EWS control unit. It is not possible to modify the individual serial number using external means.