Drive Away Protection System (EWS)
Model: EWS I/EWS II/EWS III/EWS III D E31/E34/E36/E38/E39/E46/E52/E53, Production Date: All since 1/94
After completion of this module you should be able to:
• Explain the differences in the EWS systems.
• List the components that make up the different EWS systems.
• Describe the operation of each system.
• Understand and relate the data exchange sequence between the EWS and DME.
Drive Away Protection
The first version of Drive Away Protection was installed on production vehicles 9/93 through 12/93.
Purpose of The System
The purpose of the Drive Away Protection system was to reduce vehicle theft as mandated by the European Insurance Commission to combat the high theft rate in European Countries.
This first version of the Drive Away Protection System added a circuit from the General Module to the DME. The added circuit was spliced into the existing code function from the Board Computer (BC) to the DME.
The components of the Drive Away Protection System are:
• Door Lock Switch
• General Module
• Board Computer
Door Lock Switch
The door lock switch provides a 12V (High) signal to the GM when the vehicle is locked from the outside. The switch also provides a Low signal to the GM when the vehicle is unlocked.
The GM receives the lock and unlock signals from the door lock switch and signals the DME with a 12V High signal when the vehicle is double locked or with a Low signal when this vehicle is unlocked.
The Board Computer (BC) through its’ code function provides a High signal to the DME to disallow vehicle operation or a Low signal to allow vehicle operation.
The DME looks for a High/Low signal from the BC or GM and dependent on the signal, it will either allow or prevent vehicle operation.
Principle of Operation
When the vehicle is locked from the outside, a High signal is sent to the GM from the door lock switch. The GM receives this High signal and outputs a High signal to the DME. The circuit from the GM is spliced into an existing circuit from the BC to the DME. A High signal from the GM (or BC) causes the DME to cancel the fuel and spark functions to the engine resulting in a no-start condition. The vehicle must be unlocked with the key or the code function of the BC cancelled for the DME to allow engine operation.
EWS I was installed on vehicles beginning production 1/94, replacing the original Drive Away Protection System.
Purpose of the System
The next level of compliancy with the European Insurance Commission required additional changes from the previous system. An additional component was added called the Starter Immobilization Relay. This relay module provides added theft prevention and safety features. At the time of introduction the system was referred to as Electronic Drive Away Protection which in German is Electronische Wegfahrsperre or EWS. The EWS I system consisted of the following components:
• Starter Immobilization Relay
• Door Lock Cylinders and Switch
• General Module
• Board Computer (if equipped)
• Transmission Range Switch
• DME Engine Speed Signal (Beginning 6/94 Production)
• DWA (E31)
Starter Immobilization Relay
The Starter Immobilization Relay was installed on E31, E34 and E36 vehicles.
It was in the following location:
E36 -In the relay carrier to the left of the steering column.
E31/E34 -In the “A” pillar above the footwell kick panel speaker
The Starter Immobilization Relay functions as a “Smart Relay”, a relay which receives inputs from various sources looking at the proper combination of input signals before activating a component, in this case the starter.The Starter Immobilization Relay receives input from: • Ignition Switch • General Module • Board Computer
• Trans Range Switch • DME (>6/94)
And processes output to: • Starter • DME
Door Lock Cylinders and Switch
The door lock cylinders and switch input a High/Low signal into the GM informing the GM of lock status. The signal is High when the system is in Double Lock.
The GM receives the High/Low signal from the door lock switch and outputs a High/Low signal to the Starter Immobilization Relay. A High signal indicates the vehicle is in Double Lock.
The Board Computer outputs a High/Low signal to the Starter Immobilization Relay. A High signal indicates the Code function is active.
Transmission Range Switch
The Transmission Range Switch input with automatic transmission equipped vehicles allows the Starter Immobilization Relay to provide a Neutral safety switch function. A High signal from the Trans range switch indicates the transmission is in Park or Neutral. A Low signal indicates the transmission is in a drive gear and will prevent starter operation.
The DME is both an input device (after 6/94) and an output device of the Starter Immobilization Relay.
Starting with production 6/94, the DME “TD” (engine speed) signal was added to the inputs of the Starter Immobilization Relay. This additional input allows the relay to provide a starter protection feature. The internal relay contact (starter operation) opens if the TD signal exceeds 60 Hz which equals the following engine speeds:
• 4 cylinder =1800 RPM
• 6 or 12 cylinder =1200 RPM
• 8 cylinder =900 RPM
The relay contacts will close when the exceeded Hz value drops to 5Hz below the maximum value. This is intended as a safety feature to prevent starter motor activation when the engine is running above these speeds.
The DME receives a High/Low signal from the Starter Immobilization Relay. When the signal is High, the DME does not activate injector or ignition operation.
The DWA outputs a High/Low signal to the Starter Immobilization Relay indicating the condition of the alarm system. A High signal indicates the alarm is armed, preventing vehicle starting.
Principle of Operation
The EWS Starter Immobilization Relay receives it’s inputs from the Ignition switch, GM (or DWA), BC, Trans Range Switch and the DME (after 6/94). The relay will prevent engine starting if:
• The vehicle is locked from the outside. The GM receives the High signal from the door lock switch and sends a High signal to the EWS.
• The BC Code function is set.
• A DWA High signal is received. (E31only)
• A Low signal is received from the Trans Range Switch.
• The engine speed signal from the DME exceeds 60Hz. (after 6/94)
The Ignition and injection functions of the DME are disabled and the KL50 start signal to the starter is opened to prevent starter operation.