Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Did you clean out the EGR pipe in front of the engine? It will set an EGR fault code because it clogs the flow. I'll try and find a picture.
The pipe goes from the bottom of the throttle body to the EGR oil separator, it is the large silver "J" shaped pipe in the bottom center of the picture.
So the pipe was clean? Did it have a lot of carbon?
Is that the only fault code you have? Have you tried getting the engine scanned with a more advanced scanner? It should tell you a more specific fault code such as EGR positioned fault or poor flow.
Do you know if the EGR cooler below the intake manifolds is clear as well?
Ok, is your scanner capable of reading transmission fault codes or only OBD engine faults?
The 1402 fault code is a generic OBD fault. The actual engine and transmission computers will store specific manufacture fault codes that will be more specific to the problem. You could have a DPF/exhaust problem but it would be hard to tell with a generic fault code.
The mercedes specific code might be for the Diesel Particulate Filter pressure differential sensor. This is how the computer determines how much flow in the DPF sensor but I know it can trigger a generic P1402 EGR fault.
I would suggest replacing the DPF sensor if you a more comprehensive engine scan of the fault codes is not available.
Ok, let me know what you find.