Electronic Throttle Control Module: Description and Operation

DME And EML Diagram:

EML Control Unit Location:

PURPOSE
Electronic Throttle Control (EML), replaces mechanical throttle control with an integrated power control system which uses both independent Digital Motor Electronic (DME) control modules (1.7), Electronic Transmission Control (EGS), Anti-Lock Brake (ABS), Automatic Stability Control (ASC) and Engine Drag Torque control (MSR) to calculate the proper throttle position for any given condition.

EML Throttle Inputs:

OPERATION
EML functions
^ Converting accelerator pedal position (angle), into the throttle valve opening angle.
^ Idle speed control
^ Engine speed limitation
^ Vehicle speed limitation
^ Cruise control
^ Throttle valve opening in accordance with various characteristic progression curves which are selected from a pedal characteristic map corresponding to driving status
^ Synchronization of the throttle valves
^ Interface for data exchange with other control modules (e.g. ASC, DME and EGS)
^ Safety test of important components by the EML system
^ Maintaining vehicle operability in the event of component failure by makeing available substitute values
^ Self diagnosis

Starting and Driving
When the ignition is turned on, the EML warning lamp will illuminate for one second as an indication of system activation. When the starter motor is engaged, the EML positions the throttle valves at the proper angle for starting and the DME 1.7 control units fuel injection for starting. While driving, the system regulates the throttle position according to various programs which are selected via incoming information from various sensors and control modules.

Idle
The EML control module determines engine idle speed according to input from the engine coolant temp sensor, compressor clutch status and shift indicator. Synchronization of idle throttle positions occurs if the injection signal from the DME control modules differ. The EML will close one throttle valve and open the other, in small steps, to equalize the injection signals.

Self Diagnostics
The EML system is equipped with a self-diagnostic system. Faults that occur are recognized by the control unit and stored in memory. Certain faults will also cause the EML warning lamp to illuminate on the instrument cluster. Furthermore, the EML system incorporates an emergency running program for failure of certain components and signals which will allow the vehicle to be driven to a dealership or other qualified repair facility. Diagnosis and troubleshooting of the EML system may only be carried out with the BMW diagnostic module (service tester).