SL/R231: Sleep Mode
Thread Starter
Senior Member
Joined: Oct 2019
Posts: 291
Likes: 152
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
You can tell when/if the car goes into deep sleep as the doors won’t open by touch. You need to use the key fob to unlock the doors.
My guess is the trunk might be keeping the car from going into deep sleep. (Not sure it will go into that sleep mode with doors open.)
If you get that warning light with the hood open, it’s possible that would keep the car from going into deep sleep also. I think that’s a feature MB added with the facelift cars, if the hood triggers a light. I know many of the newer MB’s have this feature, so that makes sense.
I would think if you used a battery maintainer under the (shut) hood and put the car in deep sleep it would be good for 6 months.
There are pads you can buy to help with tire flat spotting,
https://www.raceramps.com/car-storag...MyotdR1X7nXCwS
Good Luck
My guess is the trunk might be keeping the car from going into deep sleep. (Not sure it will go into that sleep mode with doors open.)
If you get that warning light with the hood open, it’s possible that would keep the car from going into deep sleep also. I think that’s a feature MB added with the facelift cars, if the hood triggers a light. I know many of the newer MB’s have this feature, so that makes sense.
I would think if you used a battery maintainer under the (shut) hood and put the car in deep sleep it would be good for 6 months.
There are pads you can buy to help with tire flat spotting,
https://www.raceramps.com/car-storag...MyotdR1X7nXCwS
Good Luck
The car appears to go to sleep even with all doors open. I'm only guessing that because the current falls to below 10 mA.
I'm using a CTEK maintainer. I don't leave it on 24/7, but only when the voltage drops a couple hundred mV.
Thanks for the link to raceramps.
Thread Starter
Senior Member
Joined: Oct 2019
Posts: 291
Likes: 152
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Thread Starter
Senior Member
Joined: Oct 2019
Posts: 291
Likes: 152
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Contrary to my other post, I guess my car never sleeps because the doors always unlock when I touch them (unless the fob is in the same pocket as my phone, which tends to block the signal).
I wonder what Tom Selleck would have done if the Ferrari had touch handles. It would have made the opening scene less dramatic. (Magnum PI reference.)
I wonder what Tom Selleck would have done if the Ferrari had touch handles. It would have made the opening scene less dramatic. (Magnum PI reference.)
MBWorld Fanatic!
Joined: Feb 2021
Posts: 1,419
Likes: 737
From: Nor-Cal
2020 GLC300 -2014 Sl550 - 1997 SL600
Double tapping the key's lock button locks the car and stops communication between the car and the key. I believe the feature is to preserve the key's battery life. It should also prevent the vehicle from being opened until the key's unlock button is pushed. Have you tried double tapping the the key's lock button? You should see a short pulse followed by a long pulse of the key's red LED.
I will run XENTRY when I get back, to give us an idea of what is actually using current in sleep mode. I think the newer cars such as the R232 may behave differently with the key fob “double click”. Supposedly it’s one of the work arounds to keep the main battery from draining on that car.
I do think there are two sleep modes for our car but XENTRY should be able to detect any change in current draw if this is the case.
Last edited by crconsulting; Dec 9, 2025 at 11:15 AM.
Thread Starter
Senior Member
Joined: Oct 2019
Posts: 291
Likes: 152
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
You’re probably right about it shutting off the FOB since you have both FOB’s. I’m traveling so don’t have access to my cars.
I will run XENTRY when I get back, to give us an idea of what is actually using current in sleep mode. I think the newer cars such as the R232 may behave differently with the key fob “double click”. Supposedly it’s one of the work arounds to keep the main battery from draining on that car.
I will run XENTRY when I get back, to give us an idea of what is actually using current in sleep mode. I think the newer cars such as the R232 may behave differently with the key fob “double click”. Supposedly it’s one of the work arounds to keep the main battery from draining on that car.
Yes, the R232 had a lot of low battery warnings that appear to have been fixed with software updates, as well as double tapping the key to stop unnecessary handshaking between car and key.
From the outset, I believed that the R232’s low voltage warning was primarily due to an excessively high low battery voltage threshold set in the programming. In other words, the computer was interpreting the battery as low because the warning was activating prematurely, even though the battery wasn’t actually low. Just my opinion, though, I have no evidence.
Although minimal, double tapping should preserve the R231's starter battery's charge as well.
Last edited by hornethandler; Dec 9, 2025 at 12:27 PM.
