Originally Posted by bill_de
I just recalled, somebody with a similar problem got the light to go out by filling the tank.
Is the MIL flashing, or just on solid?
There is a TSB for bogosity of fault code involving an obscure fuel evap sensor for build date up to late May, and another for MIL due to the processor itself for build up to late August. See WK2Jeeps.com - 2011-2016 Jeep Grand Cherokee
P0456 is the MIL Illumination P0456- Evap System Small Leak where TSB 18-034-13 Aug 15 has a flash for
vehicles older than build date 21 May (MDH 0521XX)
Typically a solid MIL will go away after mumble start/stop cycles and a solid MIL isn't as serious as flashing one.
You have two error codes, and may have something like a loose hose or similar, so I'd suggest using the warranty unless your dealer is a complete schnook.