DEF led blinking. At 25% Derate.

How long does it last? A week or two weeks?

 

It sounds like you need a new truck man. Sucks to keep having problems and worry about your ride breaking down all the time. No AC means no driving for me. Must be getting soft in my older age.

 

The last truck I had I charged the ac myself. Every two plus months. I would do it 2 or 3 times a year. No biggie.

I wouldn't live with out ac for more than a couple of days.

 

On mine yellow def light and both engine lights came on...engine derated to 55mph...turns out line and pump from def tank were leaking...replaced both and no more problems

 

Sounds like your dpf may be getting clogged. Running multiple regens cleans it just enough to pass whatever threshold needed for the system to function. I'd ask the shop to hook it to a computer and see what it says.

 

I've driven a few cascadias that would do that when pulling heavy up long grades, once you got of the grades they go back to normal. If it derates more it's time to pull over but just see how it goes, sometimes will last almost an hour before it goes back.

 

If it's a Cascadia. they have problems with the system. You might think you are doing a regen but are not.

If you are doing manuals all the time you either have a clog or the #1 can is going bad.

 

99% the emission air valve is going bad. it's on top of transmission.