Computers and Control Systems: Description and Operation

Electronic Engine Power Control

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 engine control module (ECM) by the throttle position sensor / accelerator pedal position sensor 2 (variable resistance sensors stored in one housing) that are connected to the accelerator pedal.

The accelerator pedal position (driver's intention) is a main input unit for the ECM.

Operation of the throttle valve occurs via an electric motor in the throttle valve control module.

The throttle valve is operated by the ECM according to calculated demand.

With engine off and ignition switched on, the ECM controls the throttle drive according to the throttle position sensor / accelerator pedal position sensor 2. This means, if the accelerator pedal is pressed half way, the throttle drive opens the throttle valve to the same degree; i.e. throttle valve is then opened approximately half way.

It would be incorrect to think that EPC consists of input from only one or two components. EPC is a system containing multiple inputs that contribute to recognizing, controlling and monitoring the position of the throttle valve.