For the air heater, which is to improve engine start performance at a low temperature, (1) the air heater relay does not have sufficient waterproofing and rustproofing, or (2) the air heater relay does not have sufficient waterproofing and rustproofing, and there is a glitch in the computer program that controls the air heater. If left unfixed, it may occur that the air heater relay is constantly on, and in the worst case, the air heater overheats, which could burn the surrounding electrical wiring and result in a fire.