Taking the plunge. My journey as an O/O.

Find a way to read the codes before taking it to the dealer. There are so many resources that can help save you money or point you in the right direction with a diagnosis. This could be something as simple as cleaning the 7th injector. At the very least, you will be able to tell if it's a voltage or erratic data issue, or if it's even related to the DEF system at all.

 

Watch some videos and see if you would feel comfortable doing some of the easier stuff. It's possible that you're losing a half a day or more in downtime and paying someone $400+ to just remove two bolts and spend 15 minutes cleaning a part and reinstalling it(or more if they just decide to replace the part). Sometimes bolts can be stubborn, but that's usually because they're not taken off regularly and end up seizing. It's another good reason to take them off periodically rather than wait for 300,000 miles to do it.

If you're having regen troubles, it can't hurt to check/clean the hydrocarbon doser. If you're having NOx efficiency trouble, it couldn't hurt to check/clean the DEF doser. It's not guaranteed to fix the issue, but it makes sense to do the easy stuff yourself. The only exceptions I can think of is if you're accident prone, have a bad habit of breaking things, or dropping parts into hard to reach places.

Also you'll want to read the codes in SPN/FMI format. I still have no idea what an L1 or L2 code is.

 

I found all sorts of answer to those codes. Lots of things to try before getting reamed a new butthole at a dealer.

 

I read it code be as simple as def crystals clogging the lines, pump, doser. You have to look up the codes and go from there. Rawze has a lot of info on those engines. I didn’t read anything about just on a 34. Take it to the dealer they’ll fix it.

 

My truck won't regen if there's an active fault code. If that's the case with your truck, then you should find out why NOx conversion is low. The sensor that is normally responsible for regens is the differential pressure sensor on the DPF. It is not related to NOx, it only measures the difference in pressure before and after the filter to estimate how plugged up the filter is.

It's possible that one of your NOx sensors is having trouble, but the only way to be certain is to hook up a computer and watch the ppm for irregularities. You can replace the sensors and hope it works, but if they're $500+ per sensor like Volvo, it's a lot of money to throw at a guess. Also consider that sometimes a new sensor can sometimes be faulty, especially cheap ones like you find on Amazon.

Keep your DEF tank topped off so there's less chance of poor quality causing the code. Then make sure there's no crystals building up on the doser, which messes up the spray pattern. Check for evidence of exhaust leaks, or even spray the connections with soapy water while the engine is cold. At this point, if the code persists, I would get a reset tool or take it to a good shop to get a proper diagnosis. Even with the tool, if you keep having to reset a code, then it's important to get it fixed. It just buys you more time and you don't have to stress about not making delivery, plus you can drive to any shop you want rather than whichever one is nearby before you get derated.

 

More than likely it’s a bad inlet and/or outlet nox sensor. Detroit aren’t terrible on price, about $225-$250 each. When it comes to sensors, only buy oem.