88 Euro 560SEC ASR problem
 

My 88 Euro 560SEC has been driving quite well but recently, when taking hard corners or driving a little enthusiastically, what appears to be a check engine light goes off and the pedal becomes very stiff. I was not aware that this system is drive by wire but I guess it must be, and is going into some sort of limp home mode.

For a while, this would happen and all I needed to do is turn the engine off and restart, but on the most recent occasion, the problem would not go away upon restart.

As this is not like anything that I've experienced so far. I'm wondering if anyone else as an ASR equipped W126 who may shed some light on how to diagnose the problem.

I posted to a W126 specific forum and was told that it may be a TPS and that parts are really expensive and these systems are a nightmare.

I can imagine it getting really expensive if I start throwing parts at it, so I was wondering if there is a diagnostic process that I can go through in order to trouble shoot the problem.

The 1991 USA version was a nightmare!

Always $$$ involved.

No good diagnostic tree to help with problem.

ONLY diagnostic schedule is a pin by pin test WHEN the system has completely failed!

Good luck, unless you can find a donor car to scavenge parts from.

Thanks for your response. I'll take a deep dive into the system this weekend and try to inspect each part to determine where the issue is.

I find it hard to believe that MB failed to document details on this system. Did they not use it on other models such as the W124 or W140?

I'll also try to hit some international forums to see if there is any information that can be hard from members with Euro cars as mine is an 88, which means that this system was around for a few more years abroad.