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Wildcat

Hi yall. New here. I'm a company driver for now. I drive a 2016 Volvo with a D13. I've been in it a week and a bit now. It has turned on a check engine light with a code for low NOx conversion efficiency. It has forced me to do a parked regen twice in the short time I have been in it. Also, it threatens every day or two to derate to 5 mph within
I believe it derates power to 70-80 percent at this time because i can tell i have less power as well.. But before I get to where I can pull over and request parked regen it changes its mind, lights stop blinking and power comes back. On a side note it seems to only happen when its cold,, 35 or below..
What could the problem be? I have no idea on the history of this truck. It has 426,000mi on the clock now.

I was going to check the 7th injector for carbon buildup and hope its something that simple. Its not my truck but the last thing I want to do is stop at some company recommended shop (TA, Loves, etc) where they throw a part at it and send me out the door to repeat the process again and again. If it were up to me I would do an entire tuneup,, but not sure if i could convince company to do that.. Any advice would be great. I'm still reading through the library of info on here, if there is a particular one I should read let me know! Thanks in advance.

Aleeex

Hard to diagnose a d13 over the internet. They have a plethora of issues. Could be that it needs an egr tune up (cleaning soot) or a bad air purge valve. Could be corroded wires on scr module. Could be a nox sensor.

JimT

(01-22-2021 )Wildcat Wrote: Hi yall. New here. I'm a company driver for now. I drive a 2016 Volvo with a D13. I've been in it a week and a bit now. It has turned on a check engine light with a code for low NOx conversion efficiency. It has forced me to do a parked regen twice in the short time I have been in it. Also, it threatens every day or two to derate to 5 mph within
I believe it derates power to 70-80 percent at this time because i can tell i have less power as well.. But before I get to where I can pull over and request parked regen it changes its mind, lights stop blinking and power comes back. On a side note it seems to only happen when its cold,, 35 or below..
What could the problem be? I have no idea on the history of this truck. It has 426,000mi on the clock now.

So, I have no experience with working on a D13, but I did drive one in a 2015 Volvo for a few years. However what follows is more blanket info that probably applies to any engine/truck.

Lets start with the NOx issue. NOx conversion is all about the SCR can/module. Exhaust gas comes out from the engine, through the turbo, past the 1st NOx sensor (Inlet NOx Sensor), through the DOC/DPF, through the Decomp tube where DEF is sprayed in, through the SCR can/catalyst and out the tail pipe passing a 2nd NOx sensor (Outlet NOx Sensor) as it goes. The ECM uses it's programming and sensor readings, along with measurements from the 1st NOx sensor to determine how much DEF is needed to reduce NOx to the desired levels. It's complicated and takes into account regen activity that might be producing additional NOx.

Anyway, your truck is complaining about low NOx conversion efficiency, which means Outlet NOx is not low enough compared to the Inlet NOx measurements. There could be a number of reasons for this. Poor or nonfunctioning DOC/DPF will affect the calculations, though most likely resulting in lower NOx production. Next, DEF spray could be outside of the normal resulting is an unexpected conversion result. SCR catalyst could be less effective, though unlike the DOC this isn't dependent on a special coating so usually only a problem due to damage. Finally there's the NOx sensor readings.

OK, foundation laid, here's my thoughts:

1) Faulty Outlet NOx sensor.

The ISX/cummins aftertreatment systems have had repeated problems with the Outlet NOx sensor going bad, throwing bad readings. They introduced a shield to help protect it from road spray and corrosion, but it's still a common fail point. When they go bad it's internal and they often still provide valid readings sometimes resulting in a situation like you mentioned. It's also been noted that cold temperatures make it worse (because even under normal circumstances it needs to warm up to a certain temp before it reads correctly).

2) Bad or clogged DEF valve.

These valves clog up with dried DEF or other contaminants that make it past the filter. Or they just fail to spray properly. Either way if the spray angle, pattern and volume are wrong then the NOx conversion will suffer. Also, there's a condition refereed to as an SCR or DEF volcano where dried DEF builds in the Decomp tube and causes an exhaust restriction. Dried DEF melts around 300-400 degrees (if my memory is correct) so normal operating exhaust temps should self clean any build-up and active/parked regen temps should always clean it up.

3) Exhaust leak(s)

Exhaust leaks between the turbo outlet and the tail pipe can lead to all sorts of performance problems in the aftertreatment system. Usually has a bigger impact on the DOC/DPF but, depending where the leak is, it could affect SCR conversion efficiency too.

There could be some other problems, including engine related issues, but based on your description they probably don't apply here.

I'd say most likely cause is #1, the Outlet NOx sensor (or the wires for it). Since it seems the default internal troubleshooting step for the ECM is to perform a parked regen, this should fix the issues you listed. If that's not it then additional troubleshooting needs to be done with #2 being the next likely problem area.

Again, this info is based on what I've learned trying to understand and troubleshoot my own Aftertreatment system and from what I read it's pretty much universal in design. In fact many OEM's actually use the Aftertreatment modules designed/produced by Cummins (especially post 2010) (largely with parts built by Bosch) so in many cases they are functionally identical. More recently some OEM's have built their own aftertreatment modules, but I'd be willing to bet the underlying parts and design is nearly the same.

Wildcat

(01-23-2021 )JimT Wrote: So, I have no experience with working on a D13, but I did drive one in a 2015 Volvo for a few years. However what follows is more blanket info that probably applies to any engine/truck.

Lets start with the NOx issue
...

Thank you for that layout and diagnosis. I've been reading voraciously on the subject for the past few days but you laid it out more clearly than I have seen yet. I plan to dig into it tomorrow and look for corrosion, chafing, bad connections, buildup, exhaust leaks, etc. Might go ahead and replace the outlet sensor and see if that will clear it. Just thinking here but if the def valve is restricted with buildup inhibiting the spray pattern can it be cleaned? Or must it be replaced? I also wondered... if the 7th injector wasnt injecting properly would that cause Temps to be too low to facilitate the conversion correctly? If so could it be cleaned too? Maybe silly questions but thats how we learn right?
Thanks again or the response!

JimT

yes, DEF buildup can be cleaned. The cause of such a buildup would probably be a leaky DEF valve.

DPF (7th) Injector does accumulate carbon/soot buildup leading to issues with fuel injectioning exhaust. However you'd be seeing other symptoms/issues if that were the case. Yes, the injector can be removed and it and the orifice can be cleaned of soot buildup. It's a normal part of what we all refer to as an EGR tuneup.

If regen temps were too low then you'd be seeing other faults and/or symptoms. Again, when the aftertreatment system runs into an issue it's default response is "do a parked regen". It's the equivalent to computer tech support scripts asking if you computer is plugged in, did you try turning it off and back on?

Based on your input it's my opinion that the Outlet NOx sensor (or it's wiring) is the most likely culprit. Now, if there's other symptoms or additional fault codes that you didn't mention then that could change the analysis.

As for SCR conversion, it only requires temps of a few hundred degrees. That's why a truck goes into catalyst warm-up mode when you start it up or do a lot of stop and go city driving without a heavy engine load.

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A word of caution for company drivers:

While this site is committed to helping disseminate clear and accurate information and encouraging people to learn and become hands on, you shouldn't go messing around with SOMEONE ELSE'S equipment unless you have the proper knowledge, tools AND PERMISSION to do so. While these systems, for the most part, aren't too complex or difficult to maintain, they do require some tools and knowledge. And some things, such as certain gaskets, need to be replaced when removed. I think it's great you are here looking to learn, but be responsible with how you apply what you learn. And at the end of the day, we're all just a bunch of random guys talking on the internet.

Wildcat

Ok... checked every wire and cleaned every connector I could find. Didn't find any chaffing. Removed and inspected NOx sensors, they are remarkably clean, no carbon buildup. Thats a good sign. I know they could still have internal failures but I don't think that is the issue. I also checked connections for DPF pressure sensor and tubes. Tubes are clear and connections are clean. No chaffing.
Didn't see any exhaust leaks anywhere. Good sign. Also pulled the turbo-CAC pipe to view inside as it looked like I had some oil around the boots. Its clean as a whistle. Whew. I thought it would be but checked anyways.
I checked for bad connections and chaffing around batteries (plus the little wires with fuses) and ecm. Cleaned em all but everything looks good.
I also removed the def doser to see if there was any buildup on it or internally. Its also pretty clean.
I hope messing with all the electrical connections did the trick. Hope it'll run well for me until I can get to somebody who can read a Volvo.

Anything I missed?

JimT

Visual inspection of the NOx sensors mean little. Only way to know if the NOx sensors are bad would be to use a multimeter and test the resistance and such. I don't have the procedure handy but it can be found on Cummins Quickserve.

RollinCoal

Common problems with the d13's are purge air and 7th injector, injector can be checked easy. Just need compressed air and air blower with rubber tip (there pop style injectors)