mercforhire

I have my 2011 G55 for 1.5 years and drove for about 15,000km so far( it has 175,000km now)
Recently it broke down, cranks, no start, no fuel pressure. Before it broke down completely, the car would have difficulty with cold-start, takes multiple tries, transmission shifts became slower than normal, engine power cuts out when more than 1/3 throttle is applied.
I got it towed to a shop that deals with a lot of German performance cars.
At first, I told the shop to replace the crank position sensor, then fuel pump, and still won't start.
The shop then start to really take the back electronics apart to diagnose, had to take apart the center-arm console and left rear wheel area.

The problem was fuel pump module was not supplying power to the fuel pump. I think it was from rust since my truck lived 10 years of its life in the eastern rust-belt. Thank god it was not the rear SAM unit. It was a highly difficult issue to diagnose.
In the end I replaced fuel pump(A0014706594), fuel pump module control unit(A4635452432), high pressure fuel sensor(A4639053400). Total in parts was about $1500 CAD and nearly 10 hours cost of labour($150 x 10).
Very rare issue. Just to report it here.

PeriodCorrect

Thanks for documenting this here. I am sure this will help the community in the future.


Why the thankfulness that it isn’t the rear SAM? Are they exceedingly expensive?

mercforhire

The rear SAM is a circuit board that houses the fuel pump related fuses and relays. It’s located under the center arm rest on the passenger side.
If that board goes out, it would mean the car was likely flooded at one point.
Getting a replacement is also very difficult and coding at dealer is required. It would be several thousand dollars.

mercforhire

I found this link that talks about that part in great detail.

https://www-hanshehl-de.translate.go...x_tr_pto=sc#b5