The serial data transmission is made bi-directionally via a two-wire, twisted lead between the DME and EGS control units.
The following data are transmitted from the DME to the EGS:
- Terminal 15 status
- Air conditioner compressor actuation
- Torque reduction via ignition
- Load signal with fault recognition (load signal with substitute value)
- Engine speed
- Coolant temperature
- Intake air temperature
- Road speed
- Throttle valve angle
The following data are transmitted from the EGS to the DME:
- Gear shift target gear
- Gear shift status ACTIVE
- Converter coupling switch open or closed
- Position selector lever
- OBD status of transmission management
- Torque reduction target from transmission management
- Program information
- Output speed
- Emergency running programm in EGS
The speed signal comes directly from the ABS/ASC control unit. All wheel speed signals are processed in the ABS control unit and output in the form of a square wave signal.
The ASC/MSR inputs correspond to the Bosch DME. The ASC functions within the MS41 are executed by evaluating the logical statuses at the ASC interface.
Since 01/95, every vehicle is equipped as standard with a coded vehicle immobilization system. A coded data transfer takes place between the EWS and DME control units. See also EWS functional description.
The tank bleed valve serves a managed regeneration of activated carbon filter (AKF) using scavanging air. The scavanging air drawn through the activated carbon filter is enriched with hydrocarbons (HC) according to the level of charge of the activated carbon (HC) and then fed into the engine for combustion.
The development of hydro-carbons from the fuel tank is highly dependent on:
- the fuel and ambient temperatures
- air pressure
- the fuel level within the tank
The tank bleed valve is closed when in a flow-free state. This prevents fuel vapours from the AKF reaching the intake manifold when the engine is not running.
A single-wire diagnostic interface has been introduced to meet the demands of the new diagnostic concept (similar to E38 / E39). The complete data transfer runs bi-directionally. One wire could therefore be eliminated.
A flap-controlled silencer system is installed on various M52 versions to reduce exhaust noise. To realise an active silencer syste, the exhaust system was given a controlled electro-pneumatic exhaust flap at the tail pipe of the main silencer. The DME control unit actuates an electronic switch-over valve which supplies a depression to a vacuum capsule. If the DME control unit requires the exhaust flap to be closed, it outputs an "earth" signal. The switch-over valve is actuated and the exhaust flap closed.