Freightliner cascadia dd15 fault 520342 fmi17 any idea?

Thanks for the reply, I ended up following your advice and drove it back home safely, the culprit was the def pump, once they replaced it, the code was gone. The code would only come under certain engine rpms (800 rpm for me). Which would mean the def pump was working but had a malfunction.

For any others experiencing this issue, I would get it looked at before it throws a second code (usually 520372) which will put you in a 5mph derate.

 

How much did it cost you to replace the DEF pump?