Engine check light

Take your car to auto zone or a parts store and get the code read. With the code being read you can look it up online and find out what the trouble code is. If your oil pressure gauge is maxed out then that could be your issue. But diagnosing a trouble code over the phone without knowing the code is wrong and no one can do it unless they know what the code is, and sometimes they still are wrong. I would get it read then trouble shoot it yourself. I don't see why the wiring harness would need to be replaced for the engine, also do a recall check on your car and make sure that there are no recalls for the problem that you are saying.