2013 3500 with 29k miles. Was rolling down I-70 outside Grand Junction CO and check engine light came on. Have noticed that the DEF gauge was not dropping so I put 2 gallons in and it didn't clear. Had it scanned at Autozone and P20EE came up. Is this an immediate problem or will it wait until I get home? Traveling across Utah with the family tomorrow.

Thanks.

 

I would not take the chance as it could be a number of things and if it was like mine the next thing will tell you that you will be in limp mode or something like that in the next 200 miles
Mine had to have the SCR /filter something or other changed out. They are on back order.
But the P20EE could be a few different things like a sensor or bad DEF or a number of other things.