I tried searching and everything I can find is unclear or seems to have a very specific issue that triggers the issue. I have a 2006 e500 wagon. I was getting the convenience features disabled alert for a couple days, but it would disappear after a couple minutes of driving. Checking both batteries with a multimeter resulted in the rear battery at 12v and front at 12.7v. Last night when leaving the store and backing out of my parking spot I got the ESP, ABS, Brake service alerts and only an actual ABS light on the dash. The alternator was replaced less than 5k miles ago (purchased 3k miles ago). Also the brakes were done shortly before the alternator as well as new front half shafts. Everything has been working great so far until the cold hit and the battery issue came up. Any ideas if the ESP, ABS and brake alerts could be caused by a bad battery? I am not sure when the batteries were replaced.

 

Read this.
http://www.mercedestechstore.com/pdf...2011-29-02.pdf

When the main battery is weak, the accessories (which can include the engine cooling fan!) are switched off, and the K57/2 relay engages the auxiliary battery as an emergency power source.

There was a post on batteries and coupons this past Friday in the W211 forum.

Also, turn key to position #1, press the Reset button (on the instrument cluster) three times rapidly before you start the car, and the bus voltage will display on the instrument cluster. A battery reading 12-12.3 volts is about 50% capacity or so of a new one. I purchased a Solar BA-5 battery tester for $50 and am pleased with it to date.

Crap, now I'm trying to remember if your car is a facelift car without the auxiliary battery....

 

Thank you! It does have the aux battery. I have checked bus voltage and it does seem low according to your figures. Shows 12.6-12.7v. Also the main battery appears fairly new and is not oem or AGM. Aux is oem so it may have never been replaced to date. Service history I have does not show any battery changes. Also, temps here dropped back down and now no messages on my commute home from work. Will look into replacing both battery's with AGM and report back.

 

Two thoughts:

(1) The best way to test that battery is to use the battery tester that Mercedes mentions in the cited article. The numbers you were given seem to be at odds with the numbers cited in many other articles about batteries on this forum. Apparently, using a "regular" battery tester will result in you buying a lot more batteries than you need to.

(2) If you determine that you need to replace the AUX battery (which will give you a battery light that often looks just like the main battery light, as I found out after changing the main battery, duh), here's a quick way, with a very reasonable price for an exact-size-and-shape replacement for that battery, delivered to your place with no driving around trying to find one: If you look at "all reviews" of that battery, scroll down on the first page when ordered by helpfulness, and there is a review there in which I lay out the steps for installing it. YUASA is a great brand, and for 18 months I have had no issues with the battery I installed.

(3) [Okay, a third one]: A high-quality Group 49 battery will work fine as the main, but it's probably worth the extra $20 to get the AGM one. Sears has a Die Hard Advanced Gold AGM one for $189. Pep Boys has the Bosch Platinum AGM Group 49 for $199 and currently a $10 off coupon. Advance Auto Parts has a AutoCraft Platinum AGM H8 for $189. Probably the best deal is from Amazon (especially if you have Prime free shipping): AC/Delco Group 49AGM Battery for $145.79 PLUS a 25% off coupon that you can clip right there bringing your price to $109. AC/Delco probably isn't the schwankiest brand, but for that price, who cares? If you put it in yourself, be sure to hook up that little clear hose in the trunk battery compartment to the port on the battery, so the fumes go overboard...

 

Well I have changed out the main battery. Drove around for a while and nothing popped up...until the next time I went out to the car. Error messages are back. I have not switched out the AUX battery as I am still tracking one down locally. Low battery convenience alert has not showed back up, but ESP, ABS and BRAKE malfunction alerts with only an actual ABS light on the dash appearing. It is very random when they show up (not everytime the vehicle is started) but when they do it is always shortly after start up if a sharp turn has been made. I have tried the turn wheel LR lock to lock, but that does not seem to do anything.

 

I never thought it was your main battery. That AUX battery only charges once for a short period for each time you start the car, so when it starts to go, it goes and doesn't really recharge. IF in fact the cause of your lights is due to battery issues (and it's not clear that it is) then I would be looking at the AUX.

You obviously have a preference for buying stuff locally, but I have to say it's such a PITA as compared to just having Amazon deliver it in a day or two.

 

Thank you for the reply. I replaced the main first since I did not have any signs that the aux battery was bad (not battery light or red warning) but was getting a low battery alert. That fixed that problem. Decided to do a little more research and discovered that the malfunctions only trip when the steering wheel is turned to lock on the right side. Went to empty parking lot and did some turning with wheel locked all the way left and nothing. Turned wheel to the right until lock and instantly trip alerts. Any ideas? Again getting 3 warnings everytime (ESP, ABS, BRAKE service)

 

Determined that warnings only show up when steering wheel is turned to the right to lock. Marginal right turns and anything to the left and no issues. Any ideas? Have read some about steering angle sensor (doesn't seem to throw ABS and brake warning) also some about sensor behind rotor. Again nothing mentions that it would throw all those codes. I don't think the issue is battery related as originally thought.

Warning originally came on after backing out of a parking spot one night while doing some Christmas shopping. Had been driving around town for a few hours and came on after the last stop.