The CAN Bus (Controller Area Network) connects all the control devices in the car without using a host computer. The controllers connected to this network communicate by transmitting operating data, which already contain predetermined messages to be sent via the serial data circuits. Two wires called CAN high and CAN low are used for this network. When these lines are at rest, both have 2.5v, but in operation 3.75v and 1.25v respectively.
When the U0005 OBD2 fault code is set, it means that the high-speed CAN communication bus (+) has experienced a high voltage condition.