00 S430 No Crank No Start after sitting all summer
 

Hi everyone so let me start off by saying my S430 which was passed down to me from my father had very low miles for its age, 80K to be exact. I have a few daily driver cars already so I let this one sit for the summer. I recently went to start this one up to move it in my driveway and to my surprise it was dead. So I popped opened the trunk through the latch mechanism and proceeded to trickle charge the battery. i left it for about 24 hrs trickle charge when I came to the car it wouldn't even crank over or start.I proceeded to check all prefuses and fuses in the engine compartment everything was fine. I went to feed 12v to the violet wire that goes down to the starter and it turned over and turned on for a few minutes. Stupid me decided to turn it off and back on again to no avail. Now the starter just clicks when i feed it power...
Things I noticed wrong with vehicle now...
1) Gear selector won't move, gear won't show up on dashboard either
2) Command errors in scan, no music or anything coming from sound system.
3) No communication to TCU

What I did do..
1) Order new starter and relay
2) Found a matching tcu, eis, ecu, shifter if needed.

Im trying my best to diagnose but i wanted to know if anyone had these sort of issues. This car was literally working perfectly fine not even 3 months ago i was driving it everyday, now it has so many problems. I do own another MB and a BMW and have high end scan tools. I do all the work on my cars and for others as well. If anyone can help i would greatly appreciate it.. Thank you!

The battery may still be usable, but it certainly is not yet fully charged. To fully charge a fully discharged battery takes twice the amp/hour rating of the battery. The correct battery for the W220 is about one thousand Amp/hours. That means that you need 200 hours at ten Amps!

Batteries are damaged by being fully discharged, and even more damaged by being left in a discharged state. The odds are good that you need a new battery. The car will simply not function without a good battery. The odds that you need a new starter and relay are very small.

Yes i took the battery out and left it at Advance auto which did an overnight charge. The battery tested good, cold cranking amps were good. Still no crank no start.

Water is very unusual, and might point to other serious problems, especially if the SAM where the TCU lives has been full of water. That can cause corrosion and poor connection throughout the SAM/fuse box.

It is much more common for the TCU to be full of ATF (transmission fluid). The adapter for the TCU wiring harness on the transmission leaks, allowing ATF to get into the wiring harness. The fluid then wicks up the harness and fills the TCU. It can be cleaned with brake cleaner, and usually recovers with no problem.

If the SAM cover is installed correctly and locked water never leaks into the box!

Let me add that even if the no start condition is caused by a wet SAM, your battery is likely toast. The AGM batteries don't like being fully discharged. It may test OK, but it will still give you trouble. I left the lights on at work (I know...) and then had to jump the S600 once, and the battery was never the same afterwards, despite being only two years old. I was getting odd warnings, slow cranking, all the signs of a failing battery (low voltage). I replaced the two year old battery and the car has been great since. If you're not driving it at least every two weeks (I would never let it sit a month), then get a battery tender. Best $60 you'll ever spend on this car...