EWS II system
EWS II system introduction
Changes to the European Insurance Commission regulations made it necessary to introduce a new theft protection system with greater capabilities and a higher level of security.
The EWS II system operates independent of the mechanical key. The mechanical key only makes a request of the vehicle starting system. Verification of the key electronically is required before the starting procedure is initiated.
The system features wireless communication between a programmed EEPROM housed in the ignition key and the EWS II control module. A key which is properly coded to the EWS II control module is required before starting operation continues. The EWS II and the DME control modules are synchronized through an Individual Serial Number (ISN).
The ISN, stored in the EWS II, must match that of the DME every time the ignition is switched “ON” before engine operation is allowed.
EWS II was installed on E31, E34, E36, E38 and E39 vehicles.
Major components of the EWS II system are:
• Key with Transponder
• Ring Antenna
• Transmitter/Receiver Module
• EWS II Control Module
• DME Control Module
Key with Transponder
Four keys are initially supplied with each vehicle.
Each key contains a wireless electronic chip (transponder chip). The function of the transponder is to receive and transmit data to the EWS II control module. The transponder contains a wireless read/write EEPROM in addition to a small capacitor and coil for self power capabilities.
The functions of the EEPROM are:
• Store codes for key identification, password and changing codes.
• Receive and respond to coded messages from the EWS II control module.
Power for the transponder is produced through the inductive coil and stored in the capacitor.
Each time the key is inserted into the ignition AC voltage in the antenna ring induces voltage in the inductive coil.
The Ring Antenna is an inductive coil installed around the lock cylinder which provides power for the transponder in the key and the communication link (antenna) between the key and the transmit/receive module.
The Transmitter/Receiver module supplies power to the transponder through the ring antenna and controls the flow of data between the transponder and the EWS II control module.
Data transmission between the transmitter/receiver module and the transponder takes place over a radio frequency of 125 KHz amplitude modulated AM signal.
The transmitter/receiver module converts the analog data received through the AM signal to digital data and transfers it to the EWS II control module over a single wire bi-directional data interface.
EWS II Control Module
The EWS II Control Module is linked to the BC, GM, DME, Trans Range switch and the starter for drive away protection operation. The module incorporates an integral starter relay and stores data and codes for communication with the transponder chip.
The function of the EWS II module is to provide improved drive away protection for the vehicle and it incorporates many features of previous systems:
• Lock out of the starter when the code function of the BC is set.
• Disable injection and ignition through the DME.
• Prevent starter engagement with engine running.
• Recognition of Park/Neutral position with automatic transmission.
New features that have been added:
• Disable injection, ignition and starter operation until a correct key is recognized.
• EWS and DME synchronization through the use of the ISN.
• Release of double lock when a correctly coded key is switched on.
The EWS II control module stores the following data for the key transponder inter-link:
• Key identification code- up to 10 keys.
• Key password.
• Changing code- up to 10 keys.
The DME is redesigned to incorporate the new ISN code. As of production 1/95 all DME control modules will contain the unique ISN number and will not interchange with previous DME’s. The following new features are added to the DME:
• Unique ISN assigned to DME during manufacture, it cannot be changed, altered or overwritten.
• The BC code input to the DME is eliminated.
• The DME and EWS II control module must be synchronized. The DME sends the ISN to the EWS II module which stores the number for replay to the DME.
• The ISN received from the EWS II module during start-up is compared to the internal ISN of the DME. The numbers must match before the start operation is allowed to continue.
• The ISN is sent to the DME continuously by the EWS II module with the key on.
• The DME will ignore loss of the ISN after the engine is running.
• The DME retains the ISN information from the EWS II module for 10 seconds after the ignition is switched off.