P20E8 Code for Low DEF Pressure

[Audiomediocrity]

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]

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

[JHKH]

Now having the same problem with my 2016 F250. Replaced my DEF heater due to P20BA. Now I’m getting the P20E8. You recommend checking the seals and replacing the entire pump? Any other items to check prior to the pump?

[Audiomediocrity]

I'm starting to wonder if it's this shotty aftermarket def heater. The newer truck just had a 2nd heater swapped. About a week later I put a new pump in ( Motorcraft ). Still throwing code, primed it right, but I can hear the pump like it's sucking air and liquid when I turn the key on. Might be on to the 3rd heater, ( at least the replacement was under warranty.)

[Audiomediocrity]

I put an OEM heater in, primed the new OEM pump again, and installed a new short OEM wire harness at the tank. I have an OEM DEF injector to put on tonight. Still no sign of the PID for this. Knowing pressure owuld be a great help, no/low pressure bad prime, pickup tube, seal or pump, almost reaching pressure or unstable pressure near desired limit would tell me it is likely the injector/nozzle. Will post back after replacing nozzle, but would really appreciate the PID.