DEF led blinking. At 25% Derate.

Sounds like there is another issue if the DEF level gauge is not lying to you or you're not lying to us about the "half" remark. If the system regularly runs low on def, things can become clogged and non-functioning in the DEF tank system. If it runs out or started acting up, and no proper regens have occurred lately, you will have serious issues until the system is "corrected". Until then, you can potentially expect severe loss of speed/power if it reaches a certain point, either in reality or due to malfunctioning sensors/systems.

 

What a waste and PITA that DEF crap is. Another bright idea shoved into this industry. Luckily for the time being I don't have to mess with that bs as I have an older truck. Good luck man, not a great place to be with any truck issue either...

 

The fact that you just filled it could mean that you got some contaminated DEF that is clogging the inlet screen (filter? I don't know too much about trucks). That happened to me in a Crapcadia. I filled the DEF at the TA in Wheat Ridge and made it to Vail before the light came on and the engine derated to 55. I drove a bit further and made it to Rifle without the engine derating further and parked it because I wasn't looking forward to driving at 5 MPH on those narrow shoulders on I-70.

So, all I can say from personal experience, is at least another 30 minutes to an hour.

 

I say head to a shop. If you just filled up, you could have gotten some bad DEF. My understanding is that system is designed to recognize anything that is foreign and shut itself down to protect the system.

 

If you are feeling adventurous, try pumping out your tank and refilling it. You got nothing to lose.

 

^^ this. Nothing to lose