sss1365

Seeking input from others who may have had similar.

So I am getting the common Aux Battery Malfunction message. It started when the main battery was on the way out. I replaced the main battery and was still getting the Aux Battery message. I pulled the Aux battery and measured out of the car, getting 12.23 volts. I then thought maybe the 5A fuse was bad. Checked that for Continuity with a meter and it tested as good.

Is this an error message that has to be cleared by a shop or does the system need more than 12.23 volts to recognize as a battery functioning good?

I put the Aux battery on a trickle charger and it immediately registered as at 80% while charging and an hour later as full charge. Voltage reading now is 12.93 volts.

Will reinstall and see if error clears but wanted to confirm experiences here before replacing with a new one.


Also when opening the cover under steering wheel to gain access to battery this plastic piece fell out. Can anyone advise where it goes?

Error message

Piece under dash that fell out

Other side view of piece mentioned
I am not seeing any place when looking.

NoVAe63s

12.7v is generally recognized as fully charged so it wouldn't surprise me if your code goes away. Unless when you hook it back up it quickly discharges due to an issue. Buying a new one every 3-4 years isn't uncommon, at least that's been my experience with my two Mercs.