red engine check after drived for long distance

I'd check your oil and filters first. The misleading thing about CELs these days is they turn on for everything and anything, not just the engine. It might be something as simple as your oil being low. I am a new Prius owner, so I'm not sure if it has separate sensors for all the fluids yet. I have also heard that as long as the CEL isn't blinking, whatever's wrong can be diagnosed at your earliest convenience. If it's blinking, pull over and turn off the car immediately to avoid long term, expensive damage. If you have access to an OBDII scanner, maybe try that, too?

 

It's possible that the fuel cap wasn't tightened correctly. Try that out!

 

Yes, this, too! It has to click or it could be pulling in air and throw a "large EVAP" code (p0455, I believe), which would make the CEL go off.