Electronic Power Control System (EPC) Function

Function of EPC system

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 the Engine Control Module (ECM) via two sensors for accelerator pedal position (variable resistances; stored in one housing) that are connected with 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 (throttle valve actuator) in the throttle valve control module. This is true across the entire engine speed and engine load spectrum.

The throttle valve is operated by the throttle drive according to the instructions of the Engine Control Module (ECM).

With the engine at standstill and the ignition switched on, the Engine Control Module (ECM) activates the throttle drive precisely according to the specifications of the Throttle Position (TP) Sensor. This means, if the accelerator pedal is depressed half way, the throttle drive opens the throttle valve to the same degree; i.e. throttle valve is then opened approx. half way.

With engine running (under load), the ECM can open or close the throttle valve independently of the sensor for accelerator pedal position.

This means, for example, that the throttle valve could be fully opened even though the accelerator pedal has only been depressed half way. 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 assign, control and monitor the position of the throttle valve, e.g. sensor for Throttle Position (TP) Sensor, throttle valve control module, EPC warning lamp, Engine Control Module (ECM).

Note: Components marked with * are tested via On Board Diagnostic (OBD).

- Throttle Position Sensor, Checking Throttle Position Sensor
- Throttle Valve Control Module, Checking Electronic Throttle Control Module
- Accelerator Pedal Position Sensor, Checking Accelerator Pedal Position Sensor