In-Vehicle Electronic Control System

Fail-safe is performed appropriately when an automatic driving ECU has a failure. Provided is an in-vehicle electronic control system including a recognition device that recognizes a situation outside a vehicle, a track calculation unit that calculates a track on which the vehicle travels, a failure diagnosis unit that diagnoses a failure of the track calculation unit, and an output unit that outputs a control signal used to control the vehicle, in which a control signal generated based on a brake control instruction generated by the recognition device and a control signal generated based on a track control instruction generated by the track calculation unit are input to the output unit, and when the failure diagnosis unit diagnoses that the track calculation unit has a failure, the output unit outputs a control signal generated based on the brake control instruction generated by the recognition device.