P20E8 Code for Low DEF Pressure

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Audiomediocrity
Posts: 5
Joined: Sat Jul 29, 2017 4:53 am
Vehicle: F150, 3.5 EcoBoost 365 ft-lb / 420 HP, 2016

P20E8 Code for Low DEF Pressure

Post by Audiomediocrity » Tue Aug 06, 2019 4:53 pm

This is a difficult issue to diagnose on Ford 6.7 Diesel, with several causes, and lots of expensive part swapping. It tends to come up after other modifications such as replacing the reductant heater. I think other codes suppress the P20E8 code, so that might be why it shows after doing repair work. The DEF pump is a diaphram pump that is supposed to be primed when replaced. I imagine it would be good to prime any time the DEF tank is being opened up.

P20E8 code comes on if the pump doesn't reach 51 psi in 45 seconds of pumping. There is a sensor in the pump, as well as a sensor in the delivery line going to the exhaust.

The Ford tool allows the pump to be turned on to verify spray pattern with removed DEF injector. (would love to know how to do this with Forscan)

Notable things with these repairs:
*large oring should be placed into the heater assembly, while the smaller oring should be placed on the nipple of the pump that mates to the heater assembly.
*pump should be primed with a syringe into the larger of the 2 holes that mates to the heater, until fluid comes out the area where the pump attaches to the hose that delivers fluid to the DPF on the exhaust.
Now I am trouble shooting, whether the pump works properly (only kicks on sometimes)
The throwing parts approach will cost $200+ for pump, $150 for DEF line (includes sensor) and who knows for injector.

I plan to pull pump, soak in warm water to remove crystallization, prime, reinstall...

Forscan or other help would be appreciated.

2012 Ford F350 6.7 Turbo Diesel

Audiomediocrity
Posts: 5
Joined: Sat Jul 29, 2017 4:53 am
Vehicle: F150, 3.5 EcoBoost 365 ft-lb / 420 HP, 2016

Re: P20E8 Code for Low DEF Pressure

Post by Audiomediocrity » Tue Sep 10, 2019 1:46 am

I ended up throwing parts at it, and put a new DEF pump on it. Cleared the code.

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