could be anything from either of the 2 batteries to a bad battery control unit or outdated software in the battery control unit.

 

Shouting on the forum cannot have been the only thing to cure the issue, or did you expect it go away by waiting? Anything Streetglover suggests has been done for the car, has it visited dealer service for the related recall items? Please explain what has already been done.

 

I replaced the battery in the trunk. How can I tell about the software?

 

you also have a battery under the hood, it is a backup battery for extra power for the SBC unit and other crap. only way to tell if software needs to be updated is have the dealer diagnosis the issue.

 

How can I tell about the software?

I'm afraid you need Streetglover or some his colleagues with an SDS computer to figure out the SW and updated it if necessary. I would use dealer services to check if the regulator recall concerns this car, and other fixes that should be free. At least you did not say anything has been done and an 03 car definitely should have some recall work.

 

Could it be the BCM? I have a friend who dels with a lot of Mercedes, and he was saying he has seen a lot of them go bad on this model E-Class.

 

Have a MB dealer check your VIN in VMI for all outstanding recalls and service campaigns applicable to your vehicle.

MBUSA Service Campaign 2005060008 JUN06 (e320 VIN range: A014562 – A418838) covers BCM programming and/or replacement. Note Service Campaigns do not expire therefore if included you are entitled to a no cost repair.

Upon inspection if it does turn out to be the BCM and your vehicle is not included in the campaign mention DTB P-B-54.21/155a depending on the BCM installed, they will flash or replace it. Normally a DTD does not extend past warranty however, it is a known problem and MBUA considers the original BCM defective therefore, request cost free modification.

 

I had the exact same problem with my 2004 E500, it turns out the small battery under the hood was not holding a charge and went bad causing the light to go on. I would have the battery tested. I switched mine out and the problem was fixed. Cheap fix if that is what it is.

 

most of the times it is the auxillary battery under the hood. I have seen a few BCM's fail.

 

I am having the same issue, mostly at night when the lights, etc are on. But now sometimes during the day. My dealer has never said there were any open recalls on my car, so I am going to try the front battery first, then the rear. Will probably buy an Interstate ... do you guys know the type/size I need for the small battery under the hood?

TIA,
Brian

 

Well I figured out the problem ... after replacing both my batteries it turns out that I had a bad voltage regulator. Had that replaced and all has been perfect since.

 

I thought the voltage regulator should have been part of the recall too. Perhaps it has failed another time?

 

I found this thread from last Fall and am having the same problem. How were the problems mentioned resolved? This has been recurring and seems to be fixed and starts again in a day or two. Over several visits, I have replaced both batteries, the voltage regulator and the battery control unit. After the latest BCU replacement it drove fine for a day, and light came on again this morning. The dealer I work with I generally like and they had done the 2005060008 Service Campaign to reprogram the BCU in 2006. I will talk to them to see if they will provide the new BCU at no charge. However, this has still not fixed the problem. Any suggestions? This has become quite expensive now and I still have the same problem. Thanks!

 

Sounds like it could be a alternator issue. I would check it out to see if it is putting the correct power out.

 

Had the same problem/issue with my '03 E320 a week or so ago. The dealer first said that software needed to be updated, then a week later the same error message reappeared....at that point he then re-ran another diagnositc program and said there was a bad cell in the aux battery. All has been OK since.

 

I have same problem with my '03 E320 a year ago. Add water into the aux battery. work till now.

 

This topic is still very valid.. Two weeks ago I had a RED battery light in the dash, visted the MBZ dealer, checked both battery voltage and found that the AUX battery under the hood was not holding a FULL charge. (easy fix) Replaced the battery all is well.
Until this morning.. RED Battery light in dash ( something about consumer equipment not ready) light shut off after a few seconds and has not returned all day. What now...
2003 E 320 65,500 miles

 

My problem is exact same your description.But i had no replaced the battery. It is well till now after add a few water(6 hole).

 

Hello, new to this board, I also have had this issue. 05 E500 4matic. Fortunatley I am under warranty and my R.O states:
Test Code 97507----
1 005-541-09-01 Battery (N/C)
540991 Installed updated software in BCM
97507 WMC (N/C)
541126 Battery Replace ( after check)
97507 WMC
32078 Battery light on dash light not on at this time. SDS TEST for coded, prep for test.Check BCM Performed software update, OK. Check Charging System, OK 14.4. Performed Mid Tronics test of main and aux battery. Both Failed. Replaced main battery, OK. Internal Elec Fault 023L-GRAH4

Second Page:
F** Aux Battery Failed Midtronics SMA 1-21-2009 140 PM
Cause: Electrical
541110 Condition of Backup/ Support Battery Check
Post Stamp.... Batt. Part No.
:.....Test
97507 WMC
1 211-541-00-01 Battery
541124 Backup battery replace ( after check)
97507 WMC
32078 Aux Battery Failed Midtronics Replaced Aux Battery, OK
Internal ELC Fault 023L-FQ8HC

I guess my two batteries failed and were replaced under warranty.
I am used to this problem with my Porsche due to the fact that the Pcar is a weekend only kind of car and the battery does not have constant use and charge. But the E500 is the daily driver and I am surprised that both failed after only 40 months. Glad it is under warranty but that will soon end.

Hope this adds to your info base
Joe M

 

Red Battery light on E320 merc (2008)

I had this issue and took to the local Mercedes dealer here in Spain and after the diagnostic check I was told it was the small battery in the engine compartment. This was replaced at a cost of 207 euros which seams to have solved the problem.

 

Battery Red Light on

I had this issue and took to the local Mercedes dealer here in Spain and after the diagnostic check I was told it was the small battery in the engine compartment. This was replaced at a cost of 207 euros which seams to have solved the problem.

Lesson learned:
My '05 E320 same issue, I replaced the large trunk battery in June of '14, the red light came back on in April, I was told as the new one was a non MBZ AGM so that was the red light issue so I ignored it. Yesterday first 49 degree morning and the SBS electric brakes "Failed", dealer wanted to replace the pump for $2400 (Out of 10 year warranty). It was simply this little AGM battery, I replaced it in 10 minutes, no exaggeration and viola no more brake or dash light issues. Lesson learned, Replace the SBS battery under the hood. MBZ battery was $137 in Palo Alto CA, seven dollars more than a replacement Bosch Chinese unit on Ebay. Old battery is 10.5 years old, new one is worth every penny if it lasts 6-8 years.

 

I just had this problem the last couple of days. I have an 05 CDI and the display has been red in the morning and displaying the Visit Workshop. Checked the voltage and it's reading 10 volts. Just to see if it was the auxiliary battery I put my battery tender on it the night before to see if the message would appear in the am. Started it and No message the next morning. Called dealer, they want 159.00 bucks for it so I drove over to my local Honda motorcycle dealer and bought a perfect replacement for 84.95. It's a Yuasa but the exact fit, sealed and ready to go. I have had great luck with these in my Honda Foreman. The last one I had lasted for 7 or 8 years and I don't ride very much in the winter. So don't pay the extra 75 bucks. Oh ya it took me about 5 minutes to change it out. That's including cleaning the cables with a wire brush. I did leave my battery tender on the cables plugged in to supply power when I took the old one loose. Don't know if I needed to but thought it might throw some code. Everything is great now.

 

Glad it worked out for you.

The MB workshop instructions say that the main battery should be disconnected for replacement of the aux battery because they are both on the same overall charging system loop.
Most aux batteries are swapped without the main battery being disconnected and So far no members have reported any perils from doing it that way.

 

DRNITRO

Auxiliary battery dead, I think the auxiliary battery is in the 2003-2007?. Auxiliary battery located under cabin air filter on passenger side of car under the hood, one black plastic 10MM nut, all battery bolts and nuts are 10 MM.
Remove, Take to Walmart exchange core for 10L A2 motorcycle battery $45.
Cut off red and black terminal caps to height of new terminals, vice grips in vice to hold plastic caps, cut with hacksaw.
Put red cap over (+) terminal and attach to battery. Leave (-) terminal disconnected.
Drill small hole in side of battery case and pass vent tube through the hole, seal with silicone if necessary.
Remove - battery cable from main battery in trunk.
Let car sit for awhile, I did one hour.
Connect (-)wire on auxiliary battery, let sit, I did 10 min.
Connect (-) cable on battery in trunk.
SRS only malfunction when I started car, drove car 1/4 mile turned steering wheel lock to lock 4 times and SRS reset, I read that you had to do it 5 times

 

Changed both batteries and light still stays on

 

Has the alternator and battery control module been checked?

 

Not yet doin that today