Completely different engine designs. I6 with the plugs on top VS a V8 in a hot V configuration (Exhaust comes out where the intake manifold would typically be and intakes where the exhaust manifolds would typically be. Realistically the plugs, coils, and wires on the V8 would be considerably cooler than even a normal V8 since there is no exhaust heat source near them.

 

I’ve finally changed the entire engine harness, some plugs are difficult to reach.

It’s the same reference as when it left the factory, meaning nothing has been changed. The faults are still still there.

If anyone has any idea or any clues about what to check on the ECU, I’ve opened it but I can’t see anything burnt or any broken tracks. Thanks

 

Good question. It looks like the part number is the same, but we don't know if the part itself has been improved.
I would hope they'd have a new part number for a new part.

 

Mine looks exactly the same. It could be that the wire supplier was different or that they changed the insulation plastic and it’s more resistant, but I think that if it isn’t properly protected with heat sleeves, it will end up with the same result.

This wires are only a few centimeters away from the catalytic converter, and with the engine cover on, all the heat stays there. The ventilation in the engine cover is only for the catalytic converter, but the heat rising from the engine and the radiation from the catalytic converter get trapped in the space between the coils and the engine cover.

 

Interesting observation about the engine cover. Wonder if just taking it off in general would be a help?

 

I don't think I'd do that. Under-hood aerodynamics are (or should be) carefully thought through, and you might end up overheating something else.

You'd think that if heat is the problem, they'd come up with a more heat resistant material.
My suspicion is that it has to do with recyclable materials that are required in Germany and elsewhere.

 

I think I’m going to protect the wiring with heat-resistant sleeves and then modify the cover so it looks closer to the mock-up


But first I’ll have to fix or replace the ECU...

 

I agree, I think it's also the recyclable materials, which I think is a pretty common issue for attracting rodents to chew on them too, I think....

Looking at the picture (our GLS isn't here at the moment for me to look at it), but I don't think I could actually remove it. Isn't the air filter in it? Or am I getting it confused with my old W212?

 

My dealer replaced the wiring harness because the original one had this issue.
The new one has colored wire coating on the connector end, seems different.
Does anyone experience the same issue after replacing it for a few years?