Where is the Battery Control Module Located in Trunk?
Thread Starter
Junior Member
Joined: Aug 2009
Posts: 25
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From: Canton, OH
2014 Audi Q7 SUV
Where is the Battery Control Module Located in Trunk?
Have a 2004 E500 Sport Wagon and dealer replaced the Battery Control Module to correct the battery message "Visit Workshop". Both batteries had recently been replaced and tested good. However, the next day the same warning message appeared, so dealer spent another 9 hours troubleshooting the problem, then said it was corroded connections (locations are unknown, sorry). I now question whether the old BCM is still good and want to plug it back in to test it; if it's good the dealer will get the new one back or it goes on eBay. Anyone know the exact location of the BCM in the trunk? The parts diagram from the MBUSA EPC online does not specify, it simply has an arrow pointing to the trunk area. Pulling the interior trim cover off the main battery does not reveal it. Remember, this is a wagon but info on the sedan might help too. Thanks!
Last edited by soldbydon; Aug 27, 2013 at 02:21 PM.
Thread Starter
Junior Member
Joined: Aug 2009
Posts: 25
Likes: 0
From: Canton, OH
2014 Audi Q7 SUV
Found BCM Location
Thanks for your reply, Plutoe. I did some further disassembling and found that in the wagon the battery control module is located about a foot away from the battery in the spare tire well on the rear wall (the spare tire is ahead of it). The negative ground wire leading to the main battery is attached to it so I just followed the wire to its location. It is necessary to remove the stainless steel plate below the tailgate, and remove the cosmetic covering (plastic fasteners on the sides of the tire well) that hides it from view. 
I plugged in the old BCM and confirmed that it was defective (gave the "visit workshop" message) then plugged in the new BCM and all was fine; no reprograming needed. Thanks!
I plugged in the old BCM and confirmed that it was defective (gave the "visit workshop" message) then plugged in the new BCM and all was fine; no reprograming needed. Thanks!
Last edited by soldbydon; Aug 28, 2013 at 08:40 AM.
Thread Starter
Junior Member
Joined: Aug 2009
Posts: 25
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From: Canton, OH
2014 Audi Q7 SUV
BCM in Trunk
Please see previous answer. Only source I know of other than eBay or a junkyard for a used one is the dealer, as the module does not have a generic part number on it from Bosch who makes it. List price is $438 and dealer gave me the usual 20% discount for being a member of MBCA. Given what I see on eBay - which are pricey, original versions and possibly more problem prone, I'd go with the most current version thru the dealer. MBUSA sent the dealer a part number 211-540-38-45 - which is a newer version than the original - but according to the EPC there is even a newer version that was not in stock at the time. The one they sent works fine. 
MBWorld Fanatic!
Joined: Mar 2006
Posts: 3,254
Likes: 15
From: Louisiana
03 E500 and Corvette
Please see previous answer. Only source I know of other than eBay or a junkyard for a used one is the dealer, as the module does not have a generic part number on it from Bosch who makes it. List price is $438 and dealer gave me the usual 20% discount for being a member of MBCA. Given what I see on eBay - which are pricey, original versions and possibly more problem prone, I'd go with the most current version thru the dealer. MBUSA sent the dealer a part number 211-540-38-45 - which is a newer version than the original - but according to the EPC there is even a newer version that was not in stock at the time. The one they sent works fine.
Member
Joined: Aug 2007
Posts: 128
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From: Great Britain
C320 CDI Estate, E500 4M Wagon
Vettdvr!! Good to see you're still on here. I've taken a 12-month vacation but back in the running. I miss my C5. Still have the E. You inspire me...!
Re: BCM: absolutely notorious for having corrosion!! I think mine was the root of many of my nav and other issues. The bracket/rear connector of the BCM is especially bad. I wish all W211 owners knew to remove and clean this item. I had so many issues solved by this one area. Also ran new earth (-) cables to the rear SAM area and another chassis point, I know it has helped.
Cheers all,
Smash
Re: BCM: absolutely notorious for having corrosion!! I think mine was the root of many of my nav and other issues. The bracket/rear connector of the BCM is especially bad. I wish all W211 owners knew to remove and clean this item. I had so many issues solved by this one area. Also ran new earth (-) cables to the rear SAM area and another chassis point, I know it has helped.
Cheers all,
Smash
MBWorld Fanatic!
Joined: Mar 2006
Posts: 3,254
Likes: 15
From: Louisiana
03 E500 and Corvette
Vettdvr!! Good to see you're still on here. I've taken a 12-month vacation but back in the running. I miss my C5. Still have the E. You inspire me...!
Re: BCM: absolutely notorious for having corrosion!! I think mine was the root of many of my nav and other issues. The bracket/rear connector of the BCM is especially bad. I wish all W211 owners knew to remove and clean this item. I had so many issues solved by this one area. Also ran new earth (-) cables to the rear SAM area and another chassis point, I know it has helped.
Cheers all,
Smash
Re: BCM: absolutely notorious for having corrosion!! I think mine was the root of many of my nav and other issues. The bracket/rear connector of the BCM is especially bad. I wish all W211 owners knew to remove and clean this item. I had so many issues solved by this one area. Also ran new earth (-) cables to the rear SAM area and another chassis point, I know it has helped.
Cheers all,
Smash
I gave up on my E500 when my tilt steering wheel failed 3 days before a 2500 mile trip, then on the trip the PS pump began to whine/fail, and the BCM failed. I had to drive 1300 miiles and unload the car every night to disconnect the battery so I could start the car in the morning. 3 failures in one month and the previous month the airmatic front shocks failed for the 2nd time after dealer replacement. Too many failures I gave up on MB brand.
