Some embodiments relate to a vehicle electronic controller having a microcomputer and a port expansion element, with reduced power consumption and radio noise. An MCU (microcomputer) performs determination processing that determines whether an output condition is established that is based on a signal that is input via a signal input port of the MCU. If the output condition is established, the MCU transmits a signal output instruction to a port expansion element via a communication port, and if not, the instruction is not transmitted. The port expansion element outputs a signal via a signal output port in response to an instruction from the MCU. The port expansion element automatically switches, depending on whether communication via the MCU is being suspended, between operation in a waiting mode in which the internal oscillation circuit is suspended, and operation in a normal mode in which the internal oscillation circuit is operated.