I recently purchased a very youthful looking 2016 F250 Lariat with 6.7 PS and only 20k miles. As I was taking the test drive, the check engine light came on and no other indication. The sales person had it checked out and the tech said it was an issue with the DEF system, but was able to clear the code. None the less, I purchased the truck with an exclusive "we-owe" stating they would fix anything resulting form the DEF issue. Maybe this was a huge mistake on my part...
On the 70 mile drive home the CE light came on again, then the dreaded "in 35 miles engine will be reduced to 50 mph". It counted down to about 11 miles, then the CE and the indication went away. Hmmmm…
I assumed the truck needed to be driven as it probably say for extended periods.
The CE came back on a few hundred miles later and the DEF issue came back. Ford couldn't get me in for 3 weeks, so I took it to a local shop that services Power Strokes here in Panama City, FL. They checked the DEF tank for contamination, then said the DEF pump needed to be replaced because it was intermittent and putting out insufficient pressure. Has anyone seen or heard of these or similar conditions?

 

From what I heard, they had problems early on, but supposedly improved the pumps.

https://www.powerstroke.org/threads/...f-pump.186000/

When replacing the DEF pump it is vital to confirm that the diesel emission fluid has not become contaminated with petroleum (diesel fuel). Contaminated fluid will cause very rapid failure of the new pump assembly. It is also of critical importance to clean the entire top of the DEF tank and area around the top of the pump and sending unit before removing any components. Dirt particles entering the DEF system will also cause immediate failure. Do not use any petroleum products (grease or oil) to lubricate orings and seals in the DEF system. It is recommended to only use DEF for this purpose. Before installing the 6.7 diesel exhaust fluid pump be sure to prime it using the included syringe following the factory procedure.