System Overview

DME System Diagram:

PURPOSE
The Digital Motor Electronic system (DME) 1.3, 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 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

Engine speed/position Engine speed and crankshaft position
pulse generator

Pulse generator, cylinder reference Feedback of ignition signal of a defined cylinder

Throttle switch 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)

Engine temperature sensor Temperature of engine coolant

Air flow meter Flow of intake air

Oxygen sensor Oxygen content of exhaust gas

Idle-CO potentiometer (W/O Cat.) Variable resistor (varistor) for setting the CO-content at idle speed

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)

Electronic throttle control (EML) Idle and full load signal

Electronic transmission control (EGS) Shift procedures active,torque converter clutch engaged

Range selector lever of electronic Engaged gear range
transmission control

Automatic stability control (ASC) Signal for retarding ignition timing and signal for blanking out ignition and injection

Engine drag torque control (MSR) Signal for suppressing deceleration fuel cut-out during engine drag torque control

Output Signals include:
Components Information

Injector valves Injection time

Ignition coil Ignition voltage

Idle actuator (without EML) Pulse duty factor for degree of opening

Tank ventilation valve Clock pulses for opening cycles

DME main relay DME Voltage supply

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)

Electronic transmission control EGS Engine speed signal, engine temperature, throttle angle

Electronic throttle control EML Injection signal

Automatic stability control ASC Engine speed signal

Air flow meter 5V voltage supply

Kick-down prevent Current operating status does not permit kick-down since engine speed is too high

The DME system assumes functions listed below:
^ Injection control
^ Ignition timing control
^ Closing angle control
^ Cold start control
^ Engine speed 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
^ Self-diagnosis with defect code storage

The system can also operate in conjunction with other systems such as:
^ Electronic transmission control EGS
^ Electronic throttle control EML
^ Automatic stability control ASC
^ Engine drag torque control MSR
^ Instrument cluster
^ Antitheft system DWA
^ On-board computer BC