System Overview
System Diagram:
PURPOSE
The Digital Motor Electronic system (DME) 3.3.1, 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)
Engine temperature sensor Temperature of engine coolant
Mass air mass sensor (MAF) Flow of intake air
Oxygen sensor Oxygen content of exhaust gas
Instrument cluster Vehicle speed signal
Knock sensors (2) Cylinder selective knock recognition
Ignition monitor shunt Indicates that ignition has taken place in the individual cylinder
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 transmission control Shift procedures active, torque converter clutch engaged (EGS)
Range selector lever of electronic Engaged gear range
transmission control
Automatic stability control Engine speed signal
(ASC)
Engine drag torque control Signal for suppressing deceleration
(MSR) fuel cut-out during engine drag torque control
Output Signals include:
Components Information
Injector valves Injection time
Injection disabled if secondary ignition is unsuccessful
Ignition coils 1...6 Ignition voltage
Idle actuator Pulse duty factor for degree of opening
Camshaft Adjustment Alter intake cam timing
Solenoid (VANOS)
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)
EGS control Engine speed, temperature, throttle angle
Throttle Potentiometer 5V voltage supply
The DME system assumes functions listed below:
^ Injection control
^ Ignition control with static high tension distribution
^ Dwell angle control
^ Cold start control
^ Maximum 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
^ 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)
^ Automatic stability control (ASC+T)
^ Engine drag torque control (MSR)
^ Auxiliary Throttle Valve Control (ADS 2)