I had an "auxiliary battery malfunction" message on the dash of my 2015 ML350. Had the battery replaced. Now the truck sometimes does not want to go into drive. Any experience with this?

 

Which battery was replaced? auxiliary or main?

Was the remaining battery tested for health? i.e. Cold Cranking Amperage left?

 

The auxiliary battery was replaced. Not sure if the main battery was even checked.

 

Since it has done it a few times, there should be a DTC stored in the computers.

Can you scan the vehicle with a scanner with MB-specific features? It would be great to see which codes were stored. For 2015, the auxiliary batter is still the little one hidden in the right rear (pain to get it out), correct?

 

It actually happened the first time after the mechanic brought the car to me. He checked the codes and none came up.

Another Benz site said it might be the 111 fuse. Idk

 

https://fuseandrelay.com/mercedes/166-ml-gl.html

Above is the fuse information. I doubt it is the reason, but worth following it anyways.

 

Thanks

 

Sorry I did not post the link below earlier, it took me a while to find it again

https://mbworld.org/forums/m-class-w...ml#post8479541

These car's computers/modules suffer from gremlins that can come at any time due to vibrations, moisture, user/mechanics disturbing their environment, etc.

It could be that it is just a coincidence that replacing the auxiliary battery, and the issue came the same day. Was something else opened for verification besides the rear trunk compartment where the AUX battery sits? For example,
1 - was the main battery area opened (under the passenger seat? something connected/disconnected in that area?
2 - was something disturbed near the front SAM (fuse box under the hood on the right side)

Currently, I have paused searching for a similar problem with my W212, see (https://mbworld.org/forums/e-class-w...ml#post8707959), but I have focused the problem (with forum members suggestions as well) to the Steering Control Module. When I get some free time, too busy at work to dissemble it, I will learn how to dissect the SCM (bought a used one to practice) before I open mine and follow the suggestion in the latter thread.

When it happens again, I assume the car is not moving, just open the driver's door and see if the car automatically goes into park. If it does, there is a communication problem between the shifter/stick module and the transmission module but the door switch/sensor can communicate. Also, once it is in Park, turn the car off, take the key off, locked with the keyfob (click twice), the cluster should go off/dark, unlock and start the engine. If it works, a module was hanging and it needed to be reboot it. Recall Windows computers hanging, press RESET, same thing with these cars.