Disclaimer: others are no doubt more knowledgeable than I am. Just trying to be of some help.

The Electronic Ignition System (or Switch) is the 'master' of your three SAM's (Signal Acquisition Module or Signal Actuation Module, think of those as your network computers). It is physically connected to the key lock and one example of what is does is approve your key or keyless device before you can even try to start the engine. In general it authorizes or denies more actions than one would care to realize. Want wipers on? EIS receives a signal from your wiper stalk and instructs a SAM to get power supplied to the wiper motor. Because EIS has its fingers everywhere, once it becomes faulty, seemingly and functionally unrelated gremlins start playing up. The root cause is probably a simple failure that a tech should be able to fix but MB has sought to make that difficult: an anti theft policy. Your EIS is married to your car so you can't swap one without swapping a chain of other vital components that are in the same marriage. There's folks advertising they can fix a faulty EIS, though.

The dealer won't repair an EIS. They order a new virgin one and marry it to your car, using an online factory authorization. You'd need to solidly proof the car is yours, as I found out. No one can guarantee this will solve your chain of events but reading your posts I would take the chance. As I said before a faulty EIS may obstruct a successful SDS diagnosis.

 

Thank you! I will call my local dealer and ask them if they can do it. My fingers are crossed.

 

Before I spent a couple grand on a new EIS, I would be looking really hard at the SAM modules and the CAN network. Many of the cluster warnings are a 'guilty until proven innocent' protocol. If you power up the cluster out of the car, you will have several warnings appear. These will not be cleared until the relevant module communicates via CAN that everything is OK. If an interval passes without these 'all ok' messages being received, warning messages will be displayed. The CAN hubs, especially those in the front footwells, are known for getting wet and having corrosion issues. A bad SAM can also cause warnings because it will not be reading sensor properly or not communicating the values over CAN.

As an example, you have a fuel level problem. The fuel sender is read by the rear SAM and this information is sent over CAN B to the instrument cluster so that it can control the fuel gauge and use that fuel level for range calculations. If your fuel gauge is showing empty and you know it is not, start by checking the fuel level % at the rear SAM. If that looks good, check the fuel amount at the cluster.

If you start replacing parts instead of diagnosing it, pretty soon you will have a new EIS, 3 new SAMs, a new cluster, a $10k hole in your wallet, and the car may or may not be fixed.

Also, I would differ with Frederick a bit on the management functions of the EIS. For the most part, control is decentralized. For complex features like the ABC suspension, the actual controlling is done by the relevant module, taking inputs from many different modules. Minor functions like wipers that don't have a dedicated module will be controlled by the SAMs. The EIS checks the key and, after consulting with the ECU and shifter, decides if a start will be authorized. It's other main function is to switch ignition power. If it is failing on this function, you could be losing power to the cluster and it is restarting and throwing the messages or other modules are losing power and not sending the 'all ok' messages. Still, it is expensive to replace and I would check other potential causes first.

 

I will confirm what Frederick said about providing proof of ownership. I recently had to have the EIS replaced (under warranty) for a different issue in my S550 coupe. But even though the dealership personnel know me from years of business I had to provide copies of my Registration and Driver's License before they said they could order/replace the EIS. A minor inconvenience but in many ways a strange requirement

 

I would start with the rear battery terminal cables, sounds like something is loose back there, or somebody didn’t attach a ground correctly after replacing the gas tank.

 

Thanks for chiming in, MikeJ65.
To my understanding the EIS among others acts as the gateway between the high speed and the low speed canbus systems, in my (uneducated) perception between the wiper stalk and the wiper motor. My wiper stalk consistently failed to turn on the wipers while various gremlins would instantly come to life instead. I reckoned the wiper motor, being in the engine bay, to be activated through the high speed canbus while the stalk transmits its request through the low speed bus, but I could very well be wrong there.
Any thoughts?

 

That actually makes the most sense. Battery and gas tank are less than 2 months old. Tank was replaced by the dealer and the new Mercedes battery by a local mechanic. Just as a note, as I said earlier, car is always moving when these lights and warnings appear. And throughout the show, it keeps riding.

 

The wipers are a pretty good example of how complex modern automotive systems are. In the 70's you had a wiper switch that controlled the wipers. For the R230, there are 9 modules that contribute to the wiper/washer function. The Driver's SAM controls the wiper motor, the park position heater, and reads outdoor temp, the Passenger SAM controls the washer pump, and heated nozzles, the Rear SAM reads the door switches (wipers stop when you open a door so that they don't spray water on you), the Overhead Control Panel reads the rain sensor, and finally the Steering Column module reads the wiper switch. In addition, the EIS, Central Gateway, and Cluster are also involved, as is the ESM (shifter). The EIS, Central Gateway, Cluster, and Steering Column Module are all gateway modules - connected to both CAN B and CAN C. One of those, probably the cluster, bridges speed information from CAN C to CAN B as some of the delay functions are speed sensitive. The EIS likely provides an engine start message as wipers are disabled for starting. It also provides circuit 15 power to other modules (key must be on for the wipers to work).

I would suspect that most common issue with the EIS would be its power function. If circuit 15 or 15R is not 100% reliable, strange things will start to happen as modules lose power or have low voltage.

One other note: the very early R230's did not have a Central Gateway module. This function was done by the EIS. However, in general, I don't think that the EIS does a lot of 'gateway' work. It doesn't have a lot of inputs to share and isn't the logical place to transfer most information.

 

There was a post recently about water ingress into the SAM / fusebox behind the RHS seat. It looked dry from the top but when disassembled was found to contain water, giving random behaviour like yours. Has to be worth investigating first.

 

Took another look at WIS about the EIS, just for fun, nothing else. Mike, perhaps you're giving the EIS less credit than it seems to deserve? These two WIS docs describe how EIS checks for and interprets signals from the interior bus (low speed can-bus) and processes them for authorization. S4, the stalks on our steering column, is one of the objects. Then there's the gateway function to/from the engine bus (high speed can-bus).
In this set up, when a request is made for wiping, EIS picks that up as it constantly sequentially monitors S4 and other units. If nothing with higher priority needs to be processed, EIS authorizes (not unconditionally) and signals the driver side SAM to get on with it.
Now, you mentioned that at one point in time (probable depending on SL variant) the central gateway was transferred from the EIS to somewhere else. Would that be under the dash? And would that have taken away the authorization function from EIS? This would be indicative for OP to narrow down his search for the culprit that starts and stops actions 'at will'. Because all that seems authorization related.
(Of course I agree OP needs to check more simple things first).

 

That second document is interesting, but I think it is a general document for the EIS and not applicable for the R230. It looks like the EIS was used to read column switches in some models. However, all of the R230 wiring diagrams clearly show S4 wired directly to the steering column module.

If the EIS was used to read the wiper switch in the past, I suppose it is possible that the actual wiper control algorithm is contained in the EIS and not in the driver's SAM. However, the attached WIS document strongly suggests that the Driver's SAM is gathering all of the information, making the decisions, and actuating the motor.

 

Yes, S4 and the steering wheel buttons incl the fanfare are all read through 2 wires, WIS wants me to believe. Through the steering column unit. Pitty we can't ask Heinrich, Jürgen or Heinz or whoever designed the stuff. Oh well, my expertise is largely overshadowed by my curiosity, I suppose that's okay.