The fuel injector monitor operates continuously. Detection of an open or short circuit condition of each injector is possible by comparing the actual injection signal with a target injection signal. The actual injection signal is derived from the change in injector voltage when the injector is turned off and the target injection signal is derived from an injection set flag.
A normal judgment is made when the injector voltage moves from the on to the off position i.e. on the signal edge. If the target signal and the actual signal are both set to one, a normal judgement is made. This process is repeated for each injector in firing order. A failure judgment is made when no injector signal edge is detected i.e. no change in voltage but the injector has been triggered.
