jeffn23

TLR

The electrical controls system has died starting with an error in the suspension and then the ABS. The car sat for a while and got somewhat infested with mice but I can find no wiring damage. It sits now unable to start. Or do anything else except depress me.

The problem started with the up arrow/car error coming on the dash after I had left the car undriven in the barn for a month or so. The raise button wouldn’t work and it appeared the car was bottomed out. I didn’t have time to deal with it so I left it for another couple of weeks. When I started it again, I got the same error along with the ABS ESP not functional error. So I started to do some digging.
At this point the car started just fine and would drive normally. I have a DAS system which I tried to use and found it has a low voltage in terminal 30 error which will be another plea for help in another thread. I put the DAS on two other MBs and got the same error so that problem is not with the car.
Around this time the start button didn’t work at least once so I had to use the key to start the car. After using the key once I was able to reinstall the button and it was functional for at least a couple of starts. I don’t know if this means anything but it was the beginning of a slow deterioration in, well, everything.
I bought a Launch OBD2 and it came up with bad wheel speed sensors which made sense with the ABS ESP issue. I ordered and installed new wheel sensors. I cleared the error codes with the launch and they kept coming back so I took it for a drive in the hopes it would clear the bad signal errors. I stopped during that first trip and when I turned the ignition off (using the key since the start button again stopped functioning) the engine stopped but everything else remained powered. Fan, instruments etc. I went and dropped a package off and came back out, started the car and drove home. Again the ignition only killed the engine. I had to disconnect the batteries ( front first then back) to get the car to turn off. When I reconnected the batteries strange things began to happen. The trunk closing system stopped working. The windshield wipers went on spontaneously and stopped mid cycle. Errors started showing up virtually everywhere in the Launch and things like the keyless go are now listed as not installed which is not true. And when the key is turned, the instrument lights come on, the outside temp is listed as 185F and nothing at all happens when you try to start the engine. No click, no hum, no nothing.
So here is what I have done:

Searched everywhere for information, read forums and watched youtubes.

Tested every fuse. None bad

Tested every relay. None bad

Tested and changed out the trunk battery. I tested at 350 cranking amps and wouldn’t charge past 12.2v. New one made no difference at all.

Tested the grounding from the batteries to the engine/frame. Grounding is fine every way I could check it.

Looked at every wire I could get to to see if there is damage from the mice that got in in the barn that I forgot to mention. Cleaned a bunch of mouse nests out. Washed my hands afterwards.

Found no damage to any wiring. This includes pulling out the rear SAM which seems like it contains all the functionality that has been degraded but I can find nothing wrong.

Run diagnostics and cleared codes repeatedly with the launch and they all keep coming back.

I checked the keys with the Launch and it says they are good.
The trunk lid has closed ½ way a couple of times after reconnecting the battery. And then stops. Currently no electrical system is functional. No door locks, soft closing doors, windows etc. The head unit does come on.
So I have bricked an S550. Please share your experiences and let me know what I can try next. At this point I would take it to a dealer and eat the $ but taking it to the dealer is a hate mission with a towing company I’m sure because how do you release the parking brakes just to drag it onto a flatbed?
Thanks in advance for any help I can get. Any snarky comments I deserve I’m sure so if those come with advice, so be it.
Jeff

jeffn23

I did some more searching and between konigstiger's excellent contributions and some other threads I thought maybe my the prefuse unit in the trunk was corrupted or the F38 5 amp fuse that controls the additional battery on the drivers side might have blown. With the ignition on I have 12+v to everything coming out of both prefuse boxes so it isn't that.

I tore apart the drivers side and got to the Gateway Control module and removed that thinking it might be the battery that the F38 fuse controls but it certainly wasn't. As far as I can tell there is no battery in the drivers dash connected to a fuse that could be F38. I do know that if you take out the Gateway Control and turn the ignition absolutely nothing happens. Reinstalled I got the same dash lights only when the ignition is turned back on. So, still a very pretty dead car. Any help again woud be appreciated. I think I am completely out of avenues to pursue.

BOTUS

you should NEVER attempt to get a car to stop by taking the battery off - that's a stupid thing to do on a simple car with no toys, a carburetor and points ignition - it should destroy the alternator as a minimum - to do on ANYTHING modern is really crazy, on an S class about the most insane action possible

on a tractor NEVER try to block the air intake can suck the flesh off your hand
a sensible method is to pull the fuse / relay on the fuel pump

I think you need to focus on starting and stopping of the engine - everything else is irrelevant, damaged and or confused - don't try and get rubbish like the boot open close to work that's irrelevant to what matters

reliable starting and battery charging, gear selection and then move on.... stop stressing and go bit by bit slowly - ANY diagnostics work needs battery support - you can't charge a battery and spend 30 mins with the key on the car won't cope

BOTUS

if a fault won't clear the cause is still in play - the fact mice are involved is not good news - the front SAM has far more wires than the rear one - even if there's no visible wiring damage mouse pee on a Merc electronic module will likely cause fun - electrical cleaner and ACF50 on circuit boards would make them more likely to do what they are supposed to

jeffn23

Botus, Thanks for the reply. Maybe I was unclear but the engine was not running when I disconnected the batteries. The ignition was on like if you put it in position 2 just prior to cranking on start up. Lights on, instruments all lit up. It looked like it was running but the engine was off. Had the engine not turned off without the key I'm not sure what I would have done. Given the state of this car right now I can see that happening in the future so what would be the right thing to do in that situation to prevent further damage?

Do you have a recommendation for electrical cleaner to use prior to the ACF50?

The rear SAM had a nest right on top of it so that seems like the place to start. I started to pull that out yesterday and can't seem to get it out far enough to access the cable connections in the back and under it. Does anyone have any experience or a link to removal instructions?

BOTUS

yes - I spotted after the event you had got the engine to turn off - fuel pump relay is always worth knowing where it is (safest way to make them stop)

when you say Rear SAM - the thing you see with all the fuses from inside the back seat is a separate module - this SRB clips together at right angles to the actual SAM.(with an electrical connection), tottaly out of sight between the two elements is a "rats-nest" of wiring that is tangled and snagged up - the whole unit is nightmare to remove and check. You have to pull all the boot trim out and then fight to get it to come out - where its so badly installed from the factory you risk breaking pin bush housings and their retaining clips to get it out. (Pin Bush housing is the real name for the plastic element of the multiplugs). And be VERY careful refitting the black H frame strengthening the boot floor to the top of the parcel shelf - you can trap and damage the loom very easily - remove the battery to see something and get some room to tease the wires before breaking things

second-hand bits ALL over ebay dead cheap - YOU must match the part numbers up correctly - there's about 7 different ones in there dependant upon toys and age - and the coding (aka software setup inside is specialist fun)

any brake cleaner should be enough - ACF 50 is incredible stuff - built to eat corrosion between aircraft skin and its safe on electrics and plastics


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