My check engine light use to come on and then go off. But now it has been staying on and my friend which is a mechanic say's nothing is wrong with it after inspecting it and he unhooked the battery to reprogram it. And it stayed off that entire day, but in the morning when i went outside to warm up my car it came back on so i did the whole battery thing again and it stayed off entire day again, but the next day when i went to warm up my car it was on again, so it only turns on when engine is cold i dont understand why though. If anyone know what could be wrong let me know please
