Stephanie Alexandra Diaz

For example, I'll be driving down the highway (going over 60MPH) the temps and everything will be doing great and all of a sudden my speed gauge just drops down (like it stops working) and my Check Engine light comes on but it seems like everything is still running good on her because as soon as I get her back down to under 45MPH the speed gauge pops back up and the Check Engine light goes off, it's the weirdest thing and it's been happening for a couple months now. I just don't even know where to start to try to figure out what is wrong and anytime I take it to a mechanic they can't find anything that would be wrong. I'm just confused. Any help would be appreciated.

Thanks in advance,
Stephanie