My 1993 600SL V12 frequently shows the yellow ARS light and goes into the LH mode, requiring a re-start in often heavy traffic. So far, my mechanic suspects the fuel control actuator of which there is one for each bank. The controlling actuator is supposed to cost more than $4,000. So far, I have read widely differing opinions as to the cause.

What needs to be done to diagnose the cause of the problem and repairing it?? (Short of a second mortgage)

 

I've read (on these forums) that it could be something as simple as dirty abs sensors or a faulty brake light switch ($14).
I have the same problem with that ARS light; the problem is that it's so sensitive to any kind of fluctuation in the voltage that potentially anything could set it off!
I replaced my entire wiring harness because the jacketing had deteriorated and thought that would solve the problem, but the ASR came back on with a high/low voltage maf fault code.
Damn ASR! I would check the simple things first.

 

you have a great car, however if the harness (s) have not been replaced with a non degradable insulation, then that is the first order, before anyone starts guessing??? at the problem! If I did all the replacement that various repair stations "guessed at", I would have bushel basket full of sensors, ECU's and modules!
After replacing the two engine bay harnesses, ( heat damage to wiring continuity ) the only problems have been the air particle sensor in the intake. Now when a light does come on a code reader will make sense! ( like add fluid! )