I have a 2005 E320 base model.

My car died while driving. Specifically:
1. While gassing, it lost power. Initially, gassing wouldn't get it pass 30mph. Then nothing at all, car started slowing down from inertia. Everything still on but gassing didn't rev the engine. Had to pull over.
2. Once pulled over, RPM went down to zero and engine turned off. All other electronics still working at the time.
3. Tried turning engine on. Cranked on and then immediately died within seconds as RPM went to zero.
4. Eventually (within about 10-15 minutes), trying to turn the engine on, it would only crank, engine never comes on anymore.
5. Had to get it towed about a 24mile distance.
6. (2 hours have passed total now) When unloading the car, the air suspension died and my car lowered itself (difficult time getting off truck bed without scratching the front). Power steering also died.
7. After a while (a week) car would not turn on unless I jump the battery. While jumping, the car only cranks and won't turn on. Air suspension would not rise the car. Power steering still dead.
8. I changed the crankshaft sensor thinking that was the problem. Still cranks, won't turn over.
9. After another while (a month), now jumping the car battery, electronics turn on still and sometimes I do, sometimes I don't, have an ESP error message showing for a brief second and doesn't stay showing. (time is passing because I have work and no free time).
10. Within minutes, all electronics won't turn on. Still jumping car, but not charging and whatever was charged moments ago is gone. Alarm system down, power locks down. Can't turn the key at all in the ignition at this point.

I am unsure what the problem is. No error/check engine code appeared at anytime. I have an ODBII reader for it but no code to be read. Tried reading anyways and nothing.
A bit background: prior to all this I had following:
a. There were times when gassing did not give power. Maybe a split second. Happened maybe only twice ever in previous months.
b. There was few time when convenience functions were off (message appeared) for a minute or so. Sometimes while driving. Sometimes when just getting back into the car after driving a bit. Perhaps 4 times total in previous months.
c. I have had no other error message; including no message regarding battery or esp.
d. last year I had a front-end collision where the front right headlight was. most fender stuff, not so much engine. Everything fixed by caliber.
e. tensioner pulley broke off while driving, sometime in about february or march. immediately replaced together with idle pulley.

My questions are:
1. How do I check if my battery is dead and the culprit? I know I can check voltage, etc., but all the google videos are checking a fully charge battery and it's voltage and as it turns on. What do I check for to see if the battery is simply not charging or some other connector between the battery and car is the culprit?
2. Could a dead battery have caused the car to die while driving?
3. What would be the next series of items to test and how?
4. Is it multiple problems including the battery? Should I get a new battery regardless to begin diagnosising the rest of the issues?

Any recommendations are welcomed.

 

-Bring up the voltage on the instrument cluster. There are Youtube videos showing how to do this. Search for "W211 voltage check". Your main battery should be 12.2 or above at rest, ~14v with engine running.
-Purchase an inexpensive fuel pressure gauge, connect it to your fuel rail, and check for pressure. Do a search on "2005 E320 fuel pressure" and you will find several links on troubleshooting.
-Purchase a "Solar BA-7 100-1200 CCA" battery and charge system tester. Look up the CA and/or CCA and/or the DIN ratings of your batteries. The battery tester will read voltage and give you the current amperage capacity of your batteries. If less than half the new battery rating, replace the battery.

I'm thinking a fuel issue but...you stated that on multiple occasions the "convenience functions disabled" warning came on. That indicates instability in the main electrical system; either a bad main battery or a failing alternator. You may have several issues arising at one time....

Not all OBD2 code readers will read Mercedes codes. Verify yours will.

 

Thank you. Really appreciate the recommendations and insight.