Diesel Engine Emission Codes

Diesel engine emission codes not only cause the check engine light to come on but also the “malfunction indicator light” or “MIL” will light up too. The MIL is an amber warning light that is shaped like an engine but does not have the word “engine” marked on it like the regular check engine icon. Once the MIL illuminates it’s telling you there is an emission problem.

In the video I have logged on to the detroit diesel engine diagnostics to find out which emission code is coming on. In this case it’s an EGR (exhaust gas recirculation) valve. When the EGR does not open at the correct position that’s indicating that it’s either sticking or the wrong signal is being directed to it.

What we’ve been finding is the soot levels are so high the valve mechanism in the EGR starts to stick in the wrong position. This will cause the MIL and check engine lights to come on. The EGR can be cleaned up but you can’t get it back to 100% so we usually replace it to be sure of a successful repair.

The video below will show you the EGR and what it looks like when it gets contaminated with soot.

Emission controls are here to stay and the best practice is to accept it and learn how to troubleshoot the fault. I can guarantee you it all makes sense after plugging away at these problems on a regular basis. The first essential tool is a laptop and the factory diagnostic software. Once you retrieve the code it will tell you what is wrong then you can go through the troubleshooting steps that the software provides.

Over time experience will help you get comfortable with diesel engine emission problems. Getting upset with the engine manufacturer is counter-productive and does not help the situation at all. The Mercedes diesel engines have been giving us a lot of trouble for several years. We had 5 years of warranty and when it was over it was time for us to roll up our sleeves and get into these engines head down and butt up.

There has been various problems like low fuel pressure, no regen action, EGR, turbo boost performance, DPF codes and so on. The software we use allows us to hit the “troubleshoot code” button to follow the steps. This really helps and the dealer in town is very supportive. Thanks for reading this and by all means leave a comment or a question.