SKYEG, I understand your desire to see the Grand Canyon. It's an iconic place and it's beautiful. But I agree with others here that it's simply too far to squeeze in during your layover at PHX airport.
Sedona could be a great alternative for you. Not only is it half or less the distance from Phoenix to the Grand Canyon, but it features a number of short yet still stunningly beautiful hiking trails. You'd have time to pick up a car, drive out there, hike to the top of a rocky spire or do a loop around the base of one, take lots of pictures, and get back to the airport in time for your next flight.
Best wishes!