When I drive for more than about 30-45 minutes a wrench icon pops up on my dash display. It only kicks on when I drive for a while and I tried to get the code read but he couldn't do it while my truck was running I think and when we turned it off and back on no code. I have no idea what is going on, any thoughts? And my truck is completely stock except a straight pipe but the code was throwing before the straight pipe.