'cause ya sold the truck and Mustangs don't have DEF 
P20E8..... DTC Code. Fixed
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Laughing Gas
Joined: Aug 2010
Posts: 852
Likes: 12
From: Kentucky
P20E8..... DTC Code. Fixed
I have been running this truck HARD recently. Today on my way home I got the mesage for 50 miles till my DEF was out but lucky me I returned to the yard when 1 miles left was up. Well heres where the problem starts.... I get back in the truck and it says in 0 miles till 55mph limited and the check engine light was on as well?
I took a code reader and read the code of P20E8 which means there is low pressure in the DEF pump. I reset the code and drove about 60 miles with no light.
My thinking is the truck got confused about no DEF and was trying to pump it with nothing in the tank. It must of been just the exact timing of how I stopped with 0 miles to go. Anyways... problem fixed!
Would like to add how great this truck has been this week. I've been hauling machines and material all over God's green earth and it has been nothing but great!
I took a code reader and read the code of P20E8 which means there is low pressure in the DEF pump. I reset the code and drove about 60 miles with no light. My thinking is the truck got confused about no DEF and was trying to pump it with nothing in the tank. It must of been just the exact timing of how I stopped with 0 miles to go. Anyways... problem fixed!
Would like to add how great this truck has been this week. I've been hauling machines and material all over God's green earth and it has been nothing but great!
Super Moderator
Joined: Aug 2003
Posts: 25,479
Likes: 738
From: Isanti, MN
I had the same thing happen to my truck, but I had around 200 miles to empty on the DEF. I was travelling at the time so I took it straight to the local dealer and begged them to look at it that day. They tested the system and found normal flow and determined that it was simply because of the low fluid.
Not sure exactly why, but it didn't happen again.
Not sure exactly why, but it didn't happen again.
Junior User
Joined: Nov 2010
Posts: 56
Likes: 0
I had to add DEF to my traveling checklist. Last month I was heading to the outter banks when 1/2 hour from home, I got a 800 miles of DEF left. By the time I got to the outer banks 7 hours later, it was saying 200 miles left. I was pulling a fifth wheel, so understandable. I have 10k on the truck and filled the DEF at 5k. Anyway, I had to drive a half hour to get DEF, but never did run out. Now I keep a gallon in the truck
Super Moderator
Joined: Aug 2003
Posts: 25,479
Likes: 738
From: Isanti, MN
Haha...yeah I guess you have me there. 
Seriously though, this was at around 6,000 miles and I traded around 10,500.
Seriously though, this was at around 6,000 miles and I traded around 10,500.
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Freshman User
Joined: Nov 2011
Posts: 35
Likes: 0
code hut!
My F550 2011 threw this code as well, just yesterday in fact. it said two codes but was only able to display the P20E8. I recall before that I had a msg that said low DEF or something to that effect, this time, chk engine lite, I drove 340 miles that day and no other msgs. I have not added any fluid, b/c I added some this past weekend, WTF?? I'll reset it, chk the level,
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