14 cascadia. 4 codes. Nox, poor def, derate

Just tossing ideas at the wall...

It takes two values to compute a percentage. Did you check/change the NOX input sensor as well as the output sensor?

You might try opening the one box to see if the DEF mixing tubes have burned through.

There is a test in the DDDL software that makes the DEF pump run for a fixed time in order to measure if it's working right. You have to disconnect the line and hold it in a graduated cylinder to measure how much fluid gets pumped.

Have you refilled the DEF tank after this all started happening? DEF is water soluble and you can get diluted DEF fluid sometimes. Try boxed DEF for a while and see if that helps. You can test the DEF quality in your tank with a DEF Refractometer.

Is the DEF feed line heater working?

 

Mine did that too. It got worse over the next few months.

 

Yes, the SCR catalyst was worn out. Only way to replace it is to replace the entire One-Box.

 

I can see replacing the One-Box, but why the injectors? Was the theory that over or underfueling was causing excessive emissions? I've been dealing with Emissions faults since February and currently have SPN 5246 FMI 0 and we've replaced the One-Box, Def pump, doser, lines, all harnesses (main harness, tank to pump and controller harness, and harness to sensors on the One-Box) changed output and input NoX and some temp sensors and am still derated to 5mph with SPN 5246 FMI 0. I'm at over $30,000 now and still aren't rolling. Anyone experience similar? What did you do?

 

i have brand new 1 box for this truck sitting in my garage. selling cheap $6000 cash

 

Initially they told me they were going to change just the One-Box. Then a few hours later they called again and said injectors also. Said after confirming the bad One-Box most places stop right there, but there was additional testing that Detroit said was part of the diagnosis. After completing the extra test they figured the injectors over fuelling was the cause of the One-Box failure.

 

Where are you located