Software on the ECU was original Mercedes Viano 2014

Mercedes Viano 2014

I have a mercedes 2014 Viano w639
had a piston go on me.

Had all my engine internals changed


I had all my engine internals changed so new engine. The car runs fine. Then I had a new dpf fitted new egr valve new egr cooler car run fine. I then decided to have vehicle mapped. So the map was no good. Got mapper to put original map back on run rough, bad idling, stalling etc. Mapper then put a green map on it. The vehicle run fine apart from 80 mph top speed, no kick down and 3000rpm max. So limp home mode. I got mapper to reinstall original map run rough again.

Took vehicle to Mercedes to flash the eco and reinstall original map from them. When they gave me car back they said the software on the eco was original and upto date. I took car back to them and said I won’t them to flash the eco and reprogram it with their software just in case there was some bad programming in there, which they did and vehicle still runs rough.

The technician said I need a new ecu a new dpf filter and a new pressure sensor cost £3180 and that might not fix the problem but its a starting point.

I don’t believe them

My mind tells me they have been able to read and write to the ECU so do I really need a new one also as mentioned car runs fine on green map apart from the limp home mode also dpf is 6 months old run fine on green map although dpf is not a genuine mercedes part

any ideas please


I think what they are trying to tell you is that the ECU ROM is fine but the RAM is faulty inside the ECU. But to be certain you could ask them. Anyhow, if you are not happy with the first opinion of the dealer you may take it somewhere else for a second opinion.

Are there any codes present?

I do understand your thinking. The car runs fine in limp mode. So as long as the ECU is not using signals from the sensors the car runs great. As soon as you allow the ECU to start using the the Sensors instead of the set parameter in limp mode, the engine runs bad. So if your mind is telling you the ECU is fine, replace the other components you need first and test it.