2012 Jeep Grand Cherokee
 

My gas cap light and engine is on and gives me a p0457 code. I replaced the gas cap with a factory cap, replaced the evap purge solenoid and both lights still come back on after resetting them. I had a smoke test and pump test and both passed. The dealer reset the lights after the tests and after 100 miles of driving the lights are on again. I'm at a lost. Any help would be greatly appreciated. Thanks

How many miles are on this vehicle?