tuters

When I shut my car off and try to lock it from outside it won’t lock. I have to turn the car back on and off again in order for it to lock. A few times the car has turned on but not let me shift into drive, I have to turn the car off and back on again. I’m assuming these two issues are related.
anyone else experience this?

GinDistiller

First easy thing to check would be your aux battery as they can cause all sorts of weird issues like this. Ideally check voltage w/ a multimeter, but the date code is stamped on the top once you remove the hold down and if it's pretty old I'd just start there.

PeterUbers

Are you tapping the handle to lock or using the keyfob to lock?

have you changed the battery in the keyfob?

are you using a start button to turn the vehicle on or did you pop it out and insert the key fob?

I like checking or outright replacing the aux battery as mentioned above and also check your main battery and replace the key fob battery outright - read the entire thread below on key fob batteries and improving battery connection inside the key fob.

turn the car on and off with the key fob inserted into the slot

the shifter is a know fail point as well and may need replacement.

but Occam's razor as it's applied to Mercedes-Benz indicates that there's one cause and that is most likely going to be the auxiliary battery and then secondarily could be associated with your main battery and then finally could be your key fob battery.

read through these, from the sticky:

Key fob issues

Shifter not shifting issues

The Sticky

tuters

Thanks!
I’ll check the aux and then the main battery. I thought the fob battery might be the issue but when I went to get it changed the guy said the battery was fine. I think that main of aux battery might be the issue as I left on vacation for three weeks and when I returned I tried to start my car and the battery was dead.

PeterUbers

make sure you improve the contacts for the key fob battery - discussed in the thread above mentioned

PeterUbers

keep this car on a battery tender like a ctek if not driving more than a week ... trust me it'll save you drama

GinDistiller

Yep, one visit for tinting my front windows took out my aux battery haha. Probably had to have the key on for some time moving them up and down. Although it was 8 years old according to the date code...

I've seen people say 'oh, you'll get a warning on the dash' - no, only sometimes. No warnings for me, finally noticed when my cruise control stopped working and I tested it at under 12v...

PeterUbers

And a battery tender does not also charge the aux battery - that only charges when the car is running.

some good advice from @CaliBenzDriver in this thread about dual battery tenders

https://mbworld.org/forums/e-class-w...tery-also.html

CaliBenzDriver

Sorry to read about your issues with Inam going to guess... KEYLESSG.

you will want to scan your car to confirm a patern of CAN-B faults.

In these conditions your chassis is waiting for an excuse to DRAIN YOUR BATTERY kaput by disabling low-power sleeping modes.
This lack of supervision is so fleepin' low tech. A bunch of modules going banana endlessly.

Use your prefered scanner with code descriptions.