Originally Posted by maddenma

Ok, still fighting with this 6 months later. Car has been at MB Manhattan (MB Factory Store) for this 10 times now and they are still scratching their heads. The independent shop I was using threw in the towel after a few weeks of getting nowhere. Dealer replaced the front KG antenna (throwing codes) and Central Gateway (not throwing codes itself, but the devices connected to it complain about "implausible data" in their own codes). No effect. Notably, the KG never throws a code, but it is always affected. The other symptoms either appear or not, seemingly dependent only on the mood of the car at the time and even the KG symptoms themselves can vary.

Key fobs aren't the issue. They can't turn on the radio or wipers. Doesn't matter if they are sense-able by the vehicle or not, the symptoms will still present themselves without the key in range of the car (wipers go to top of stroke over night with the car a block away and the key behind a 2' thick stone wall). Also doesn't matter if I try to open it with the door handle or the key fob buttons. My phone is also no where near the key when I attempt to open it. Dealer also pulled all the carpets to check for any water leaks or signs of flood damage. No evidence of water found.

I've been taking videos lately for the dealer, because of course it never occurs when they have it, though I've been dropping it off every Monday and picking it up every Friday for the last 8 weeks (10 visits for this complaint in total). They are here: https://www.dropbox.com/sh/yl7ud94oc...1MVVWU4na?dl=0. If you watch a few of these, you'll see the variation in the symptoms and probably laugh at its antics. I'm not finding it so amusing myself anymore, but I certainly can see the humor in it.

Symptoms include:

• · Does not unlock car with door handle or key fob buttons
• · Unlocks car, but then won’t recognize that the key is in the vehicle and won’t allow the car to start
• · Turns on the COMAND system display and other functions related to the COMAND screen and audio without unlocking the door (it shouldn’t turn this on ever). COMAND turns back off as soon as you open the driver’s door from the outside with the hard key – as if I was exiting the vehicle instead of entering it.
• · Unlocks and opens the rear cargo door without allowing you to unlock the rest of the vehicle after many attempts with the door handle or key fob buttons while still allowing the tailgate to operate normally.
• · Allows you in the car with either the door handle or key fob, but may or may not allow the car to start with either the push button or inserting the key fob.
• · Allows you in the car with either the door handle or key AND allows the car to start, but will not select any gear for the transmission. Remains in Park.
• · Decides key is not in the car after 90 minutes of Interstate 95 driving, forcing me to pull off the road to reset the system by turning the car off, opening and closing the driver’s door, and then restarting the car (only happened once).
• · Several combinations of these symptoms have been seen (e.g. unlocks car, turns on radio, but then won’t go into gear once started).
• · If the switch for the rain-sensing wipers is left in the 1st or 2nd intermittent position over night, and if the Keyless Go symptoms occur, then the wipers will be parked at the top of their stroke when I come out to the car as if I had shut the car off before the wipers finished their stroke.

CG and front KG antenna have already been replaced. If anyone has some thoughts on what to try next, I'm interested in hearing them. Though there are no codes for it present, I'm probably going to have them swap out the KG module as I've already come to the conclusion we're going to have to replace some otherwise perfectly functioning parts just to find the problem, but there's a lot of expensive, non-returnable stuff in there to try just throwing parts at it hoping to get lucky.

Originally Posted by maddenma

If anyone has some thoughts on what to try next, I'm interested in hearing them.

Originally Posted by konigstiger

If the only dealership in the country owned and operated by MB has not already done so, request Shop Foreman or Lead Tech open a PTSS case for MB technical support.

Originally Posted by maddenma

Well, here we are 11 months later and still no cure. Clearly not just a Keyless Go issue, as COMAND, Instrument Panel, Trans Select, and Engine Start are all affected with an occasional occurrence of the instrument panel or COMAND turning on in the middle of the night, flattening the battery -- which significantly elevates its importance to me.

The other thing I've discovered since my last post on this is that the problem is temperature sensitive. After May of last year, it largely stopped, starting back up again in October when the temp started dropping below 60F at night.

At this point the Central Gateway, Keyless Go Module, and both KG antennas have been replaced. Main Battery has been replaced twice now due to "voltages all over the place" -- whatever that actually means in detail.

I'm starting to think that perhaps this is related to the auxiliary battery or the accessory power relay. I've had no warning notice on the dash about the aux battery, but when I pulled it this morning I noticed that I still had no warning light with it removed. Should I have gotten one?

These are cheap things compared to the previous guesses MB Manhattan has made. Also, don't require programming them into the vehicle, so I'm planning to replace them as a wild guess. While I can find references to the relay and a part number, there doesn't seem to be one in the rear SAM of my vehicle where various charts seem to have suggested it should be. Anyone know for sure where this is on a 2011 S212? Which SAM and what position?

Originally Posted by maddenma

JA few days later, I had an unusually extended bout with trying to get the vehicle to recognize the key. After 5 attempts, the vehicle told me to REMOVE START BUTTON AND INSERT KEY.

Yup. Head slapping moment right there... I had pulled it out before on demand, but always replaced it the next time I got in the car. After leaving it out it's been 5 months since the slightest difficulty with it. A $50, apparently electrically inert, plastic button.

Assuming there's no wireless batteryless chip in that START button, it's got to be something with that switch. I may fix it, I may not at this point. I can insert that key a whole bunch of times for the $1000+ that switch is going to cost to replace, so I may never confirm this for certain, but it's really clear where the trouble was. Just thought someone with a similar issue may want to look at the ignition switch before yanking keyless go modules and other very expensive bits. Or just pull and leave out the START button....

Originally Posted by Sunnyslope48

Modern cars communicate between the various modules on LAN lines (not sure what MB names their communications system(s)) and anything tied to any module or circuit can bring that LAN down, and when the failure to communicate happens, you have a problem, or many problems. Since your problems are repeatable in the sense that they happen on a fairly consistent basis, that would allow someone to monitor and record those LAN communications and see when they're gong down and then to find the culprit. Of course, changing parts is a very poor way to discover the cause of the problem, much as if you went to your doctor complaining of not feeling well and they decided to start transplanting various parts and pieces of your body until you felt better!

I would think that MB Manhattan has all the right equipment, technology and trained techs to know what to test and has the equipment to do the testing. I certainly hope they aren't just changing parts hoping to find a BINGO.

Originally Posted by maddenma

On the Keyless Go issues, the symptoms:

Generally speaking, the Keyless Go system frequently will not unlock the car or allow it to start and is exhibiting other symptoms as well. This is generally at first use after the vehicle has been sitting overnight,

Documented Keyless Go symptoms include:

• Does not unlock car with door handle or key fob buttons (obviously common)
• Unlocks car, but then won’t recognize that the key is in the vehicle and won’t allow the car to start (also not uncommon)
• Will unlock and open the rear cargo door without allowing you to unlock the rest of the vehicle after many attempts with the door handle or key fob buttons while still allowing the tailgate to operate normally.·
• Allows you in the car with either the door handle or key fob, but may or may not allow the car to start with either the push button or inserting the key fob.

Originally Posted by BellBiv

OP, did you ever figure this out? I have a 2017 W205 and I am getting the EXACT symptoms that you mentioned. Wonder if I should replace the car's battery or something.