CaliBenzDriver

On my '14 facelift when the MAIN goes flat/disconnected, AUX is tasked with locking the steering only as the driver door is opened.

Previously ESL module was activated at each driving cycle to lock the bottom of the steering column. The module was famously associated with NoCrank/NoStart when it failed to handshake with the EIS ignition key module.

Facelift changed that a bit by no longer locking every drive cycle and physically locking the steering rack instead of steering column.

Smoke6948

Hi all,

I've been through the entire string of messages here.

I have a 2012 E-350 Bluetech diesel.

Need to find the auxiliary battery.

Does anyone know where to look? I've read it is in the trunk and also it is under the hood.

Please help.

Thanks in advance...

Smoke6948 in Florida...

kajtek1

I believe 2012 don't have ECO stop function, therefore it comes with small aux battery for shifting backup.
Those are mounted in dashboard on driver side.

JJR

Don't restrict your search to MB forums. Do a Google search under: year make model and Auxiliary Battery. That way you'll get access to all clubs & forums, including UK, Austrailia, Canada, etc, plus YouTube, etc.

konigstiger

MB part # 000000004039 should also cross reference to aftermarket See attachment, you can start comparison shopping here: https://www.fcpeuro.com/Mercedes~Benz-parts/

thewhitegorilla

Has anyone had problems with low voltage to the auxiliary battery? the dealer installed a new battery ($270) and still the error message, and then the next day the alternator light came on. They rescheduled me as the time was running out to come back at a later date. the mechanic told me that there was a corrosion some where in the wiring but where? anybody know how that wire is routed on a 2010 ml350?
Thanks
Charles

thewhitegorilla

I forgot to add he said it was getting only 5 volts, we have had this error for some time, I replaced the battery and it went out and then back on intermittently until it never went out again and the wife quit bugging me about it,
Thanks
Charles

CaliBenzDriver

Damn.... a 5V charging voltage, 10V drop lost on the way: that's huge!
The rear AUX gets its charging voltage through the nearby single fuse.

The problem is not caused by trunk new AUX but by something else... like the ECU pegging the ALT output thereby shorting both batteries.

Double check :
(GND strap chassis-engine)
Aged ALT regulator
Wild ECU "yoyo voltage" control

You want to pull wiring diagram of voltage distribution to help narrow down where lays your 10 volts drop issue.

Scan the chassis to get a fresh set of fault codes.

With the dashlight ON, the issue is related to alternator output being too low.

Further DVM poking required to trace things out. A simple reboot may help cure that temporarily - As in don't go drive across country right away after getting your car out of the shop.
🤞