System Overview

System Diagram:

PURPOSE
The Digital Motor Electronic system (DME) 1.7, provides precise control of fuel injection and ignition systems to ensure optimum performance and strict emissions compliance.

OPERATION
Various engine sensors and other systems (i.e.. air conditioning, auto transmission etc.) supply the DME control unit with operating information. The DME control unit processes this information and sends control signals to adjust injector pulse width, ignition timing and influence other important systems and components.

Inputs signals include:
Components Information

Digital motor electronics Voltage supply for a part of the digital
DME main relay motor electronics

Crankshaft Sensor Engine speed and crankshaft position

Camshaft Sensor Feedback of ignition signal of a defined cylinder

Throttle potentiometer Position of throttle valve

Intake temperature sensor Temperature of intake air (in this way, the air density which is reduced as the temperature increases is taken into consideration)

Knock sensor Knock condition

Engine temperature sensor Temperature of engine coolant

Air flow sensor Flow of intake air

Oxygen sensor Oxygen content of exhaust gas

Instrument cluster Vehicle speed signal

A/C, defroster or air Air conditioner in operation
recirculation switch

A/C compressor A/C compressor in operation

Battery Current system voltage

Terminal 15 Ignition switched on

On-board computer (BC) Entered code (engine operation not possible)

Antitheft system (DWA) Antitheft system armed (engine operation not possible)

Range selector lever of Engaged gear range
electronic transmission control


Output Signals include:
Components Information

Injector valves Injection time

Ignition coils 1...4 Ignition voltage

Idle actuator Pulse duty factor for degree of opening

Tank ventilation valve Clock pulses for opening cycles

Digital motor electronics main DME Voltage supply
relay

A/C compressor relay Switching off A/C compressor

Electrical fuel pump relay Activation voltage

Oxygen sensor heating relay Activation voltage

Instrument cluster Engine speed signal, injection signal (for fuel consumption indicator), fault lamp (US only)

Air flow sensor 5V voltage supply

Throttle Potentiometer 5V voltage supply

Differential Air Intake System Flap Control
(DISA)

The DME system assumes functions listed below:
^ Injection control
^ Ignition control with static high tension distribution
^ Dwell angle control
^ Cold start control
^ Idle speed control
^ Acceleration enrichment
^ Dynamic torque deceleration fuel cut-out
^ Adaptive emission (lambda) control
^ Adaptive fuel evaporation control
^ Adaptive idle speed control
^ Characteristic map switchover for EH transmission
^ Limited (emergency) operation control
^ Relay control
^ A/C compressor cut-out
^ Protection functions for catalytic converter and engine
^ Self-diagnosis with defect code storage

The system can also operate in conjunction with other systems such as:
^ Instrument cluster
^ Antitheft system DWA
^ On-board computer BC