2 days ago I woke up to my 2010 W212 E350 4matic with a dead battery. The car sat for about 5-6 days, figured the battery is dead but did my due diligence, charged and tested the battery and it is completely fine. Checked current draw with a locked car, hood latches closed and everything off. While the current does drop to ~10mAmps after a short while it randomly spikes to ~500mAmps briefly and drops back down to ~10mAmps in a few seconds. When the current spikes I notice the engine fan turns on and does a couple revolutions. The weird thing is at some point the display on the cluster turns on with the odometer and sometimes says "PRE-SAFE functions limited". The thing is the car is not equipped with a front facing radar for Distronic and does not have a front facing camera. It does have front facing parking sensors but I highly doubt they have anything to do with it. As the Pre-safe message says to look at the owners manual the manual says there is a menu to turn off pre-safe but I have no such menu since the car has no radar system.
Has anyone had this message show up while not having the system? Any clues as to why and how could the cluster display a fault for a system it does not have equipped?

 

All good questions!

Your chassis has reached its crisis mode. Your MB specialist should be able to help regain normal control.
The causes of that issue are often not obvious. It may include water penetrations.

 

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This is my W212 of 2014 facelift fully asleep draw. K2 relay is off and should be off when car is sleeping.

Below is 15 minutes duration.




the 5 milliamps is not always 5 milliamps, there is always self-checking happening and can be up to 11 milliamps.
If 500 milliamps kick you get once in a while, probably there is a module not yet into deep sleep.



If engine been running, to go to deep sleep mode it can be up to 6 hours.


Below : The time it took my car to go to deep sleep, when engine OFF already occured 12+ hours ago and I open the door to wake up the car, and let it goes back to deep sleep.
12 minutes is the typical wait.




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This is W204 of 2010. Nothing above 75 miliamps kick.

The lower "zoomed" file are the consumption spikes which I separate from the normal 4-5 milliamps and merge them each with 1 second extra interval as zero milliamps separator,
to see how long in seconds these up to 75 milliamps spike last.



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Test if during 10 milliamps, is the K2 relay already OFF ?
Below is one of the 2 outputs of K2 relay. Easy to access.


The K2 relay when OFF may not show zero volts, because modules downstream of it has capacitors, so you will read 0.7 volts or so.
You can remove this low ghost voltage by loading it with a bulb for 2 seconds.


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If your K2 relay is already OFF and you get that 500 mA spikes, them it is from modules powered by Circuit 30 ( always ON ).

Find circuit 30 on the list of link below, Front SAM and Rear SAM fuse box
Front & Rear SAM has modules inside which is always ON by duty.

Front SAM : https://mbworld.org/forums/e-class-w...ml#post8810002

Rear SAM : https://mbworld.org/forums/e-class-w...ml#post8810004

Door module is known to go bad and does not go to deep sleep.



Good luck......

 

> STOCK DRAIN TYPES...
In the prior post: Master Surya is showing a brilliant "Drained by Parking" study from half-dozen sleepless circuit-30 CAN-B modules.

A chassis in crisis will get higher current draws more frequently equal faster drain.

Batteries are further upset by "Drained by Driving" to render CAN modules more unstable and slow.


> SHADES of GREY...
Base on the above, a good chassis has multiple standard ways to drain its AGM batteries (Low Main drains AUX).

The draining involves multiple causes ganged up in a snowball... The solution is the same in the opposite way: multiple fixes.

Repairs require practical troubleshooting to sort out sources.


> QUICK WORKAROUND ...
To simply circumvent drain issues you can LOCK THE DOORS (even at home!) and use a FLOAT CHARGER on the main battery.

Headaches be gone!


To help yourself, survey chassis faults using MS recommended Launch scanner.

 

Holy moly that is a lot of very useful info, thanks a bunch. Will post an update if I figure out the issue. I am still baffled by the warning message for a system the car doesn't have and I have never seen anything like it during my career. I Will dig through it soon enough.

 

As I have thought about a similar workaround I have gifted that car to my elderly father and do not want to bother him with a fix like that .

 

Low Bat condition can produce weird DTC, just like Power Loss.
So always note but ignore DTC after battery went flat and when battery charged OK, clear all DTCs and scan again.
If the said DTC never came back, that is Low Power./Power Loss caused.

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Here is an example of me plugging off a relay on purpose, I wanted to see how smart the modules are.

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Relay J removal. Ignore my soft DTC for alternator/starter. I disconnected my alternator LIN on purpose.



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Relay K removed


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RELAY R, a very upstream relay powering a few relays downstream of it.



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As I finally found the time to look into it I found some interesting things. Now I started with the fan turning on for a couple revolutions. Unplugged the fan, the current draw still appeared but was down from 0.450 amps to about 0.250 amps. Checked the fan connector and I found I have constant power on the fan power line. Checked the relays in the engine compartment but none of them seems to be responsible. To me it is not logical to have constant power to the fan especially with how big the fuse for it should be. Looked over several schematics for the relays but can not find a dedicated relay. Is it a separate relay or is it combined/ named in a weird way?
The other thing I found was when the car wakes up relay N turns on. Tried unplugging it as well but the consumption was still high. What module turns on said relay?

As there are other electronics behaving unreasonably like the cluster turning on and off while the car is locked and is sometimes flickering while changing gears I am thinking of taking it off and unplugging it as well.
Had some DTCs about the front driver door window switch not being learned but it relearned normally and unplugging the door module still did nothing.

The most odd thing is that when walking around the car when everything is locked pulling on the trunk switch imitates the consumption and all other complaints like turning on the cluster display, turning on the N relay, the fan does its couple of revolutions, the consumption goes to the one I was previously measuring (about 0.450-0.500amps). It being a switch and not a mechanical lever seems reasonable to me to be waking the car up. As I do not have the proper tools to take off the trunk liner I could not measure for short between the pins of the trunk switch but unplugging the switch itself did nothing and the car is still waking up.

 

Relay N is Circuit 87M. That meant it is engine related.



Relay N also send signal to radiator fan M4/7. The power of M4/7 the two fat wires, the positive is direct fed from F32 fuse F154 or fuse F151, depending on our car model, option etc etc.
M4/7 fan has built in PWM speed controller, so if you asking its dedicated relay, it has one inside it and is a solid state, not mechanical one like relay N.




If in my car, W2212.065, Relay N feed power to these fuses :


You need to see the full copy of Front SAM ( 10 pages/sheets ) and the engine computer N3/10 schematic ( 2 or 3 pages/sheet ) specific to your engine type, which I beleive if 2010 is an M272 ...yes ?
To see what are the fuses served by Relay N. The basic design of MB for W212 engine fuses assignment is similar, albeit not the same between engines, but very similar.


You wrote :
The most odd thing is that when walking around the car when everything is locked pulling on the trunk switch imitates the consumption and all other complaints like turning on the cluster display, turning on the N relay, the fan does its couple of revolutions, the consumption goes to the one I was previously measuring (about 0.450-0.500amps). It being a switch and not a mechanical lever seems reasonable to me to be waking the car up. As I do not have the proper tools to take off the trunk liner I could not measure for short between the pins of the trunk switch but unplugging the switch itself did nothing and the car is still waking up.
I do not know if you have Keyless Go option or not, but the trunk open button is an electric signal button , not mechanical , on my W212.065 and I am sure it is the same for your W212.
The key slot, for trunk, that is pure mechanical, as back up. So when you try to press it ( trunk open button/lever ), it then wakes up the car a bit.
If car is Keyless Go option, the FOB key proximity to the trunk switch or any 4 door handles, will automatically allow doors to be UNLOCK with simply a touch, and then you can open the door manually grip+pull like it is never locked.