Apparatus and method for detecting fault in glow plug

In method and apparatus for detecting a fault in a glow plug provided in a diesel engine, a possibility of a fault in the glow plug is determined without utilizing a forced change in the state of energization of the glow plug for the purpose of diagnosis, before the presence of a fault in the glow plug is determined by utilizing the forced change in the state of energization of the glow plug. The process of determining the presence of the fault is not executed if it is determined in the process of determining the possibility of the fault that there is no possibility of a fault in the glow plug.