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BMW: Drive Away Protection System

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A lot of you folks are probably still working old BMW models with equipped with EWS Immobilizer systems. In BMW, the purpose of the Drive Away Protection system (EWS) was to reduce vehicle theft as mandated by the European Insurance Commission to combat the high theft rate in European. When working on BMWs, from time to time, these EWS control modules are either needed to be replaced or coded or programmed. In this article, we will go through the differences between EWS alignment, EWS coding and programming.

Several generations of EWS had been implemented on BMW vehicles since last decades. Here is a summary of different generations of EWS over the years:

On EWS I, the Starter Immobilization Relay was used to receive signals from Ignition Switch, door lock switch (General Module), Board Computer and Transmission Range Switch. Based on the signals, the Relay will either enable or disable the starter and Digital Motor Electronics (DME) for ignition and injection operation. On EWS II, a key transponder and a EWS control module are used. the transponder is used to energize the EWS control module and sends key identification code to EWS control module. If the code is correct, EWS control module will activate the starter. Then EWS control module sends a unique Individual Serial Number (ISN) to DME for verification, if the ISN matches the one in DME, the drive away protection is canceled and injection and ignition is enabled. Otherwise, the vehicle will be immobilized. On EWS III (3.2), the major changes over the EWS II are a modified control module, revised wiring and the addition of the clutch switch input. All other operations are similar for EWS III are similar to EWS II. On EWS III (3.3) and EWS III D, the new "Rolling Codes" are used instead of a unique ISN code on communication between EWS and DME to add greater theft protection than previous systems. The Rolling Code is basically a changing ISN code which is different everytime the vehicle enters the start sequence.

Replacement Procedure

Keys:Up to 6 additional keys may be ordered as replacement keys. The EWS control module is codeable for only 10 keys (4 delivered with vehicle and 6 replacement)

EWS Control Module:When replacing EWSII Control Module with a new, it must be VIN specific in order to recognize key ID codes. In addition, the EWS control module must be ZCS coded and then perform a synchronization with the DME in order to be fully functional. The EWS Control Module must be synchronized with the DME so that it stores the correct ISN/Rolling Code. There is no limit to the number of times the ISN/Rolling Codes may be changed in the EWS Control Module. ZCS coding on the EWS control module can only be performed using OEM scan tool while some OE-level aftermarket scan tools can perform DME-EWS synchronization (see figure).

DME Control Module: The DME Control Module is not ordered VIN specific and must be programmed during replacement. After programming, the ISN or Rolling Codes are stored to the DME permanently and is not changeable.

Key Activation: Keys that are lost or stolen may be deactivated using OE-level scanner. Any key may be disabled except for the key in the ignition. The lost or stolen key can be identified by the identification of the remaining keys. There is no limit to the number of times a key can be activated or deactivated.