What causes epc light to come on?

All drive-by-wire cars (starting from 1995-2013) has an EPC light. EPC stands for Electronic Power Control which is controlled by the ECU (Engine Control Unit). This is a computerized hardware device with software to control all sub modules in the car that is connected by either an OBD II (on-board Diagnostics II) or Can Bus (Controller Area Network). Any input from these sub modules on the drive-train can activate the EPC circuit especially if the reason for sending its signals to the ECU, could cause damage to the engine. For example, if the car runs out of oil, or if the emissions exceed the prescribed level ect.... the sensor will send a signal to the ECU which will activate EPC circuit, cut power to the engine (limp mode). Limp mode signifies there is a problem and should be investigated. If not fixed, the EPC can ause the engine not to start unless corrective action is taken. See EPC solution at http://volkswagen-polo-highline.blogspot.com