Electronic Throttle Actuator: Description and Operation

Electronic Power Control

Function of "EPC" System

For "EPC", the throttle valve is not operated by a cable from the accelerator pedal. There is no mechanical connection between the accelerator pedal and the throttle valve.

The position of the accelerator pedal is communicated to Motronic Engine Control Module (ECM) J220 by Throttle Drive Angle Sensor 1 (for Electronic Power Control (EPC)) G187/Throttle Drive Angle Sensor 2 (for Electronic Power Control (EPC)) G188 (variable resistances; stored in one housing) that are connected with the accelerator pedal.

The accelerator pedal position (drivers intention) is a main input unit for the Motronic Engine Control Module (ECM) J220.

Operation of the throttle valve occurs by an electric motor ( Throttle Drive (for Electronic Power Control (EPC)) G186 ) in the Throttle Valve Control Module J338. This is true across the entire engine speed and engine load spectrum.

Throttle valve is operated by Throttle Drive (for Electronic Power Control (EPC)) G186 according to specifications of Motronic Engine Control Module (ECM) J220.

With engine off and ignition switched on, Motronic Engine Control Module (ECM) J220 controls the Throttle Drive (for Electronic Power Control (EPC)) G186 exactly according to specifications of Throttle Drive Angle Sensor 1 (for Electronic Power Control (EPC)) G187/Throttle Drive Angle Sensor 2 (for Electronic Power Control (EPC)) G188. This means, if the accelerator pedal is depressed halfway, the Throttle Drive (for Electronic Power Control (EPC)) G186 opens the throttle valve to the same degree; i.e. throttle valve is then opened approx. halfway.

With engine running (under load), Motronic Engine Control Module (ECM) J220 can open or close the throttle valve independently of Throttle Drive Angle Sensor 1 (for Electronic Power Control (EPC)) G187 / Throttle Drive Angle Sensor 2 (for Electronic Power Control (EPC)) G188.

This means, for example, that the throttle valve could be fully opened even though the accelerator pedal has only been depressed halfway. This has the advantage of preventing torque losses at the throttle valve.

In addition to this, it results in significantly better values relative to emissions and consumption under certain load conditions.

It would be incorrect to think that "EPC" consists of only one or two components. "EPC" is much more of a system containing all components that contribute to recognizing, controlling and monitoring the position of the throttle valve.
- Observe safety precautions.
- Observe rules for cleanliness.