Check engine light
 

Check engine light came on after driving for about an hour on the interstate. After about 10 minutes the speedometer dropped to zero and the odometer went blank. They came back for a minute and then went off again. After I stopped for a stop sign the engine revved up and then dropped back down. The Toyota dealership says that the code could be 4 different things and they can't get it to do it again. Any advice would be appreciated.

Year of car and engine type, 4 cylinder or V-6?

What were the codes?