Battery dies in 2 days
 

Hi there, my 2005 E320 wagon began showing a low battery error in the dash. Then it was dead on morning. I removed the battery which was only 3 years old. Went and got another one and that one drained in 3 days. I clearly have a problem with something electronic staying on when the car is off. I am going to go look with a meter to see what the Off current is out of the battery. We were having an issue before this happened with the rear door latch not shutting correctly. It used to have a motor that pulls the latch in after you shut it. That stopped a few weeks ago and then the battery started to drain. Just wondering if anyone has seen a similar scenario. The car has 125K on it. IT was fine until we took it to a shop for new rear Air bags. Since that shop worked on the car we have had issues. It took 5 trips to the shop to get Airbags to stay full. The shop said there was a rash of Arnote defective bags. They replaced one side 3 times. Wondering if there is wiring in the area they might have hurt with all that work.

Bcm is dead.

Body control module ?
 

So where is this lovely piece of electronics hiding? Can one buy a good service manual for a W211. I own 6 cars and this is my first MB. Don't know much about it.
Thanks

It's about $300 to replace. $150 for parts and another $150 for labor. Could be a bad alternator as well...or voltage regulator. Pull some codes.

Battery control module. Check in the trunk. There is a black box with a mass cable attached to it. Check it out.

This is a diy forum. Labor costs nothing to urself.

Need to check for current consumption before replacing parts. For tailgate lock (fastener) replacement shop part # 2117400136, 2117400235 used, and/or current 1647400635 used/new. See attachments.

The MB service manual is the WIS. You can buy a knock off version on eBay for around $6.60. A little hard to figure out. Once you do though, you can pull up documents like above. The legit version is MB's startek, but that costs $60 for 24 hours of access.

https://www.ebay.com/itm/Latest-2019-Mercedes-WIS-ASRA-EPC-Service-Repair-Workshop-Manual-Full-version/123679649919

https://www.startekinfo.com/StarTek/subscribe.jsp

Really? WOW!! How insightful. Labor costs nothing if you do it yourself! Didn't know that. Thanks for opening our eyes.

Don't try to be a hero.

Bob, it sounds like the problem is your tailgate handle/latch and not the battery. I have an R320 with a sticky tailgate handle that does not spring back anymore. As a result if someone tries to open the tailgate manually (by hand), the handles sticks open and it continues to drain the battery. The handle needs to snap back into place in order to stop draining the battery. You mentioned your problem started after you had a tailgate rear latch issue. Start there and inspect the handle carefully. If its sticking, then replace it and get it working properly or only open the tailgate with the fob or interior button. If its not the handle, figure out why your latch was not closing properly. It will continue to drain power if its not closed properly.

Had same problem with my 2004 E320 wagon. researched & found could be a problem with multicontour seat power wire, but that wasn't it on mine, also wasn't the BCM, so I paid Mercedes for up to 2 hrs diagnosis & they found 14 milliamp parasitic draw traced to Comand head unit. charged me for .7 hrs & Said it was a $700-800 part & 2 hrs labor to replace. I checked around & got a new head unit from Husker Auto in Lincoln NE for $520 then replaced it myself. Believe it was a Mercedes Reman unit as there was a $400 core charge which Husker refunded when I returned the old unit in prepaid box they provided. Solved problem and the radio music sounds better, also tunes more distant stations with the new radio.(we live in area of poor reception) Don