Hoo boy, I just lived through this one. My car is fine now. No more ASR/Check Engine lights. But it cost me nearly 3K to get there. Much of that money was wasted on misdiagnosis. I learned there are more than a dozen inputs and/or faults that can trigger this event. This is compounded by the known problem with disintegrating insulation on the engine wire harness. What you NEED to find is a tech with access to the Mercedes factory diagnostic system who has the patience and access to your car enough to track down the fault. In my case, the first diagnostic unit that was used to read the stored fault codes was insufficient. It only showed up as a live fault on the Mercedes unit.

Check the thread I started about my car in the tech help forum. Do a search for ASR/"limp home" mode. In my case it turned out to be a failed transmission shift position sensor. I wasted my money replacing the throttle actuator and the Electronic Accelerator Control Module. Spend your money on diagnosis first. But on my car it could only be found when the sensor had failed enough to trigger the fault pretty much whenever I drove the car.

The tech who helped me solve my problem printed out a block diagram of the engine management system from the service manual. It shows the many inputs that make up the system. It is worth tracking down; it gives a good indication of how expensive it can be to just try plugging in components to fix the problem. By the way, I have a serviceable throttle actuator and EACM if you want to buy them!

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Mark Stetson
1995 E320 Wagon Moonstone Grey/Parchment 106K mi.
2007 E63 AMG Graphite/designo 75K mi