Hello,
2015 F350 Dually, Crew Cab, Flatbed. Purchased with about 150,000 miles in November. Driving it home CEL came on. When home, code P20E8 was identified. We replaced the DEF Pump last month, and truck was running great, no CEL. Hooked a trailer up calling it trailer #1 for this conversation, and about 3 hours into a 4 hour round trip CEL came on. Code read P20E9. Trailer #1 was removed, and a different trailer calling it trailer #2 was hooked up. About one hour in to a three hour round trip message, exact wording I don't have, but in 50 miles, speed limited to 50 mph. In 50 miles, message, speed limit basically on next power cycle (again, can't recall exact wording). Got home no issues, unhooked trailer, leaving truck running, brought down to my shop area to back in, and CEL went off. Checked with reader,and nothing. Hooked up Trailer #2 on Wednesday, and 1/12/ hours into a four+ hour round trip message blinked DPF Cleaning, or whatever that message is, then CEL light came on. I only ever see cleaning message for like a second. Once home, I verified with reader, P20E9. Removed trailer, but light is still on. I have driven about 50 miles, but it is still on. I have researched these forums, and posted a message on FB, but I so far haven't seen any clear direction. I do see suggestions of monitoring pressure. Is there a tool I can get that can give me that information?

It seems ironic that this happened only when a trailer is on, but when driving longer trips, that is what I usually have.
I can clear the code, but obviously that is not going to take me anywhere.
Looking for advice/assistance.

Thank You

 

bad pump out of the box. Comes on when towing since the higher temps require more def.

 

Is there a way to monitor what the current pressure is, or what it thinks it is to trigger the too high code?

 

I don't have the manual to tell you that information. Perhaps you can find a video on it.

 

P20E8 (PCM) - Reductant Pressure Too Low - you just replaced the pump and now you are getting P20E9 (PCM) - Reductant Pressure Too High. That's an odd outcome.

According to the 2016 service manual P20E9 suggests Damaged Reductant Injector or Damaged Reductant Pressure Sensor.

First step is to check Urea for concentration and contamination. If that checks out then the SCR dosing test is required to determine if the injector is operating within spec. If the injector is operating within spec the next step is to replace the reductant pump.

At this point it's possible during the pump replacement contamination was introduced into the DEF. Cheap and easy first step.......drain and clean the tank and refill with fresh DEF and see if the concern returns?