The Ews 2 (Electronic Vehicle Immobilization System 2) is a sophisticated anti-theft system introduced by BMW in 1995. Designed to meet stringent European insurance regulations, EWS 2 significantly improved vehicle security compared to its predecessor. This article delves into the inner workings of EWS 2, outlining its components, operation, and key programming procedures.
How EWS 2 Works: A Step-by-Step Breakdown
EWS 2 employs wireless communication between a transponder chip embedded in the ignition key and the EWS 2 control module. This communication, along with a unique identification number (ISN), ensures only authorized keys can start the engine. Here’s a detailed breakdown of the starting sequence:
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Key Insertion and Power Up: When the key is inserted and turned to the “ON” position, the transmitter/receiver module sends a 125kHz AM signal to the ring antenna around the ignition cylinder. This signal powers the transponder chip within the key.
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Key Identification: The energized transponder transmits its unique identification code back to the transmitter/receiver module. This code is then converted to a digital signal and sent to the EWS 2 control module for verification.
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Password Exchange: If the key code is valid, the EWS 2 module sends a digital password to the transponder. The transponder verifies this password and, if correct, sends a changing code back to the EWS 2 module. This dynamic exchange enhances security.
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Starter Engagement and ISN Synchronization: Upon successful verification of the changing code, the EWS 2 module activates the starter relay. Simultaneously, it transmits the ISN to the DME (Digital Motor Electronics) control module. The DME compares this ISN with its own stored ISN. Only if the ISNs match will the DME enable fuel injection and ignition, allowing the engine to start.
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Continuous Communication: Even after the engine starts, the EWS 2 module continuously sends the ISN to the DME to maintain security. The system also generates a new changing code for the next starting sequence, further enhancing theft protection. The DME will ignore a loss of ISN signal after the engine is running and retains the ISN for 10 seconds after the ignition is turned off. Restarting the vehicle within this timeframe bypasses the key identification process.
Key Components of the EWS 2 System
EWS 2 comprises several crucial components working in concert:
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Key with Transponder: Each key contains a transponder chip with a unique identification code, password, and changing code stored in its EEPROM. This includes valet and wallet keys.
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Ring Antenna: This antenna, surrounding the ignition lock cylinder, powers the transponder and facilitates communication between the key and the transmitter/receiver module.
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Transmitter/Receiver Module: This module manages the data flow between the transponder and the EWS 2 control module, converting analog AM signals to digital data.
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EWS 2 Control Module: This module verifies key codes, manages password exchange, controls starter engagement, and synchronizes with the DME via the ISN. It also incorporates the starter relay and features drive-away protection functionalities.
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DME Control Module: The DME stores a unique ISN that must match the ISN from the EWS 2 module for the engine to start. This module controls fuel injection and ignition.
EWS 2 Module Replacement and Key Programming
Replacing EWS 2 components requires careful attention:
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EWS 2 Control Module: Replacement modules are VIN-specific and require coding to match the vehicle’s key codes. The module stores the VIN and the Central Coding Key (ZCS) and needs to be synchronized with the DME after replacement.
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DME Control Module: While not VIN-specific, a new DME needs programming, and its ISN must be transferred to the EWS 2 module.
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Key Activation/Deactivation: Lost or stolen keys can be deactivated using diagnostic software, preventing them from starting the vehicle while still allowing door unlocking. Up to ten keys can be programmed to a single EWS II module, with four keys provided with the vehicle. Six additional keys can be ordered.
