W222 "Auxiliary Battery Malfunction"

barry jones

Senior Member
Joined
Oct 7, 2008
Messages
599
Reaction score
119
Location
Warrington
Your Mercedes
2016, LWB W222 AMG Line S-Class S350d - W415 Citan Van too :)
Car is a 2016 S350d that I've owned for just over 3 years.

A few months ago, when opening and getting into the car, an audiable "ding" was heard and a yellow battery icon and "start engine" (or words to that effect) were displayed. This didn't happen every time and so I assumed it was just the battery getting old and I planned to swap it at some point as the car ran fine.

Then, two or three weeks ago, I got a new warning come up on the dash after the car was started that said "Auxiliary battery malfunction". but not everytime I used the car.

The issue disabled Distronic, stop/start (which never really worked much anyway) and a few other functions such as lane assist etc. and so I rang Mobilo and a technician came out within 2 hours and ran the checks and said it was the main battery that was the actual issue. He went off to the local dealers and got me a new battery (£265.00 - ouch :) )

He returned and fitted the battery, and all was good. Everything worked, including stop/start, which must require a decent battery I assume to function due to the load of stopping and starting.

Did a journey into Manchester and when I got back in the car to come back, the same warning appeared. I rang the technician (He had rung me earlier in the day to advise of his arrival time so I had the number!!) He told me that his computer had made no mention of an auxiliary battery issue but it may now be an issue with capacitor which the W222 has or an auxiliary battery, which I have no idea where it is on the car.

Does anyone have any ideas where there may be an auxiliary battery or capacitor that may be causing the issue? The warning doesn't come on all the time, but when it does, driving wihout distronic is a pain!!
 

Dunhamkid

Senior Member
Joined
Nov 25, 2005
Messages
76
Reaction score
8
Location
Outside Chester
Your Mercedes
W222 2015 S350 Bluetec
Car is a 2016 S350d that I've owned for just over 3 years.

A few months ago, when opening and getting into the car, an audiable "ding" was heard and a yellow battery icon and "start engine" (or words to that effect) were displayed. This didn't happen every time and so I assumed it was just the battery getting old and I planned to swap it at some point as the car ran fine.

Then, two or three weeks ago, I got a new warning come up on the dash after the car was started that said "Auxiliary battery malfunction". but not everytime I used the car.

The issue disabled Distronic, stop/start (which never really worked much anyway) and a few other functions such as lane assist etc. and so I rang Mobilo and a technician came out within 2 hours and ran the checks and said it was the main battery that was the actual issue. He went off to the local dealers and got me a new battery (£265.00 - ouch :) )

He returned and fitted the battery, and all was good. Everything worked, including stop/start, which must require a decent battery I assume to function due to the load of stopping and starting.

Did a journey into Manchester and when I got back in the car to come back, the same warning appeared. I rang the technician (He had rung me earlier in the day to advise of his arrival time so I had the number!!) He told me that his computer had made no mention of an auxiliary battery issue but it may now be an issue with capacitor which the W222 has or an auxiliary battery, which I have no idea where it is on the car.

Does anyone have any ideas where there may be an auxiliary battery or capacitor that may be causing the issue? The warning doesn't come on all the time, but when it does, driving wihout distronic is a pain!!
I have the same car and the auxiliary battery is in the boot on the offside. Not too difficult to change if you have small hands!!
 
OP
barry jones

barry jones

Senior Member
Joined
Oct 7, 2008
Messages
599
Reaction score
119
Location
Warrington
Your Mercedes
2016, LWB W222 AMG Line S-Class S350d - W415 Citan Van too :)
  • Thread Starter
  • Thread starter
  • #3
Car went in for its' scheduled service and they replaced the auxilliary battery... all working well now and the stop/start is actually functioning better than it ever has since I bought the car!!
 


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