SCR SYSTEM FAULT

Thanks for the reply.

We did remove the flex pipe and there was a little but of crystals inside. Also, the doser valve had some white on it and it seemed like it leaked out too. Perhaps, the doser valve is bad?

I topped up def with 8 litres when it was showing full. Drove 1400 miles after my fill up and the guage still shows full.

 

Now my mechanic is saying it needs a doser valve and a def pump. Def pump is quite expensive.

 

What test did they do to determine that the pump was faulty? I would expect code 5392(DEF pump loss of prime) to pop up if it were faulty.

I had a shop replace pretty much everything except the lines, when the problem was a corroded terminal/fuse between the battery and the aftertreatment control unit. $8000 and 2 months later, they gave up and towed it to Volvo, who replaced the $10 part to fix it.

Based on my experiences, I'd say to replace the doser valve first and go from there. Maybe the pump can burn out from being blocked at the valve or something, but let them explain that to you instead of just blindly throwing parts at it. I would want to find out why they want the pump replaced.

 

I'm headed to Arkansas and I'm in Ohio just woke up to dash saying scr system altered or fault detected would it help to do a manual regen

 

Do you see any codes under diagnostic menu.

 

Has anybody some news about this issue? A month ago I replaced the two nox sensors and now I got this same problem.

 

Anyone have any issues with scr derate with no codes on dash at all. Truck shut down after derate because def heater, acm codes. Towed truck to shop and parked inside. Next day all codes disappear but truck still in derate mode. Did manual regen, filter was already clean but did anyways. Still scr derate will not go away.

 

When I had a bad inlet NOx sensor, I had a similar problem. When I shut down the truck, I cleared the codes. The next morning I went to drive off without any check lights showing on the dash, and couldn't get over 5 mph. But the derate went away after I ran a forced regen. Make sure the regen completes and doesn't get interrupted. Another difference is that I was using an OTR performance tool to clear the codes and perform regens, so my codes didn't just go away on their own. I'm not sure if that matters or not.

 

Try the battery kill swith for 30 seconds and back on. I've gotten the same code before when I had taken an extended period of time off and forgot to switch inverter and batteries off. Then had to jump the batteries to start the truck.