Powertrain Management: Description and Operation

PURPOSE
The Digital Motor Electronic (DME) system (3.3), provides precise control of fuel injection, ignition and emission control 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 the input signals and sends output signals for control of injector pulse width, ignition timing, and other important system functions.

System Diagram:

Input signals include:
^ Engine Speed
^ Reference Mark Signal
^ Air Mass (Hot Film)
^ Intake Air Temperature
^ Coolant Temperature
^ Cylinder Identification
^ Secondary Ignition
^ Throttle Position
^ Knock Sensor
^ Lambda Signal
^ Battery Voltage
^ Vehicle Speed
^ Gear Position (Auto Trans. only)
^ A/C Signal
^ On-Board Computer (OBC)

Output Signals include:
^ Fuel Injection Control
^ Ignition Control
^ Idle Speed Control
^ Fuel Pump Control
^ Evaporative Control

ON-BOARD DIAGNOSTICS
In the event of a DME system malfunction, circuit information will be stored in the internal memory of the DME control unit. Intermittent failures are stored with a record of the failure frequency.

The DME control unit is able to store up to thirty malfunctions and will give priority to those items which can cause the vehicle to exceed exhaust emission standards. In addition to being stored in memory, an emissions-related failure will cause the "Check Engine" light to illuminate on the instrument cluster.

ADAPTIVE CONTROL
The DME control unit has adaptive idle speed and air/fuel mixture capabilities. The control unit continuously compares the programmed data for idle control and air fuel mixture with the input values.

If a deviation occurs, the new input values are superimposed and stored in the programmed data map. As a result, new output signals are sent to the idle control valve and or to the injectors. This allows the DME control unit to correct the idle speed or injector pulse width for break-in wear or slight air leaks which might occur in the systems.

If power is interrupted to the control unit, new adaptation takes place within several minutes of engine operation.