hey guys my mustangs service engine doesn't come on and i know it has to come on because my cars having misfire issues. When i turn the cluster on without starting the car the light is on so the bulb is good so does anybody know if there's a fuse or relay that controls it?

 

Rather than rely on the light, hook up a handheld OBDII scanner that has a datalogger or live view. It will be obvious which cylinder is having the misfire then or what is causing it.

 

+1. Not all misfires will cause the check engine light to com on.