Electronic Engine Power Control

Electronic Engine Power Control (EPC) is the automobile industry's "Fly by Wire" system. In EPC systems, a vehicle's ECM uses information from the Throttle Valve Control Module which integrates throttle position sensor (TPS) and electric throttle-valve drive element, also information from the accelerator pedal position sensor (APP sensors), wheel speed sensors, vehicle speed sensor and a variety of other sensors to determine how to adjust electric throttle-valve drive element. The accelerator pedal position sensor and the throttle position sensor work together to translate user input into throttle plate movement. These sensors have utilized potentiometers that worked as voltage dividers. Voltage dividers use a resistive element and a wiper arm to "divide" an input voltage (called a reference voltage). They then send this "divided" voltage to the ECM, which uses it to command the position of the electric throttle-valve drive element. The drive element is a DC servomotor, which acts on the throttle-valve shaft (Throttle Plate).

The driver command is detected by a redundant sensor system in the accelerator-pedal module, and the signal is sent to the ECM. It calculates the required cylinder charge, based on the current engine operating point, and then the throttle valve control module regulates the opening angle of the electric throttle-valve drive element by means of the throttle-valve position sensor. The redundancy incorporated in both the accelerator-pedal module and the throttle valve control module is part of the EPC monitoring concept for avoiding malfunctions. In the event of a malfunction while the engine is running, the ECM will command "ON" an EPC warning light and at the same time, command "ON" the MIL also a Diagnostic Trouble Code (DTC) is stored in the ECM memory.