Hello, I'm looking for help because I've been working on power consumption for a long time.

After turning off, shutting down and going into sleep mode, the car reaches a quiescent current (0.02-0.05A)


after some time (a few hours) it wakes up, quiescent current 2-3A (we connect the recorder, the current consumption is visible and CAN-B wakes up [interior])


All fuses checked, no change in power consumption. I managed to turn off the power consumption once by disconnecting the roof control panel, I think by accident.


From my observations, the problem usually occurs after starting the car, running the engine, and then turning it off. If we reset it by disconnecting the battery, the problem disappears.

 

disconnecting all batteries (chassis reboot) does help solve networking issues for couple days.

It can be a very positive step when combined with a battery float-charge.

Modules in charge of draining battery while parked are CAN-B members.

 

At the least, you must first verify if when car is in deep sleep mode, where the K2 relay DOES get shut off.
If K2 relay does not get shut off, car is not in deep sleep mode.
It takes up to 6 hours for the car to deep sleep if engine were ever running the hours before.

My car M276.8 3.0 Turbo is 7 milliamps in deep sleep mode, K2 relay off.
Make sure you use in-line DMM ammeter function to detect such small current, but also becareful the 10A fuse in the DMM will blow once you open the car door,
because power consumtion is higher than 10 amps for a while.

You can "jumper" the DMM ammeter input for the first 15 or so minutes or when you see it is below 4 amps of current....... remove the jumper cable.

This is how to "jumper" a DMM ammeter, the extra black wire I use, will carry approx 50% of the load.
Yes, you need to have 4mm banana jack type connector or you can always improvise.



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PREFUSE F32
The easiest K2 point ( circuit 30g ) to inspect for deep sleep marked in green, use DMM or test light. Best test light of 30 to 120 mA to remove the surface voltage, there is some ghost voltage there and DMM may see 0.3 to 3 volts after K2 shut down.
There is another K2 output ( circuit 30g) in the same F32 prefuse box, but at the bottom, not easy to access.




If you car does not go to deep sleep in 6 hours, at the least you will know there is something else to troubleshoot, aside from the bad module which woke up out of the blue and sucking
2 - 3 amps.

K2 is a big relay in F32 prefuse. It gives power to all circuit of power wire called 30g. G = switched, aka uses relay.
If always hot, always have power , MB called it Circuit 30. No relay whatsoever is being used, can not kill power to Circuit 30, unless battery removed.

There are many modules having Circuit 30 as power, but its activation is by other means , mainly by CAN BUS or some command signal hardwire type.

So you need to split the troubleshooting, the bad module is under Circuit 30 or 30g ?


Give me your VIN and I can give you suitable wiring diagram for your car.

Good luck..........

 

turn on 30g in night, but i dont have idea why. I flash new program rear sam but its still not working.

 

Target the device which can wake up K2/30g.
Example : Door or trunk handle, when not locked, opening doors or trunk will wake up the car. Thus bad door lock could be a suspect.
- Surely key FOB must be as far away as possible
- Any Mercedes Apps or Emergency Feature using 3G network on the car ? This is known to keep bus awake and car wont sleep
- Driver seat bad module , also this is known to keep bus awake and car wont sleep


Also if your bad module or culprit is worth 2-3 amps, it will be easy to find even with thermal camera, if not millivolts drop at the fuse.
I assume you have a closed garage where you can do overnight test safely with your trunk lock being fooled ( to access rear SAM ) , hood ( has workshop mode ) but best you fool both of the latches and all 4 doors lock fooled.

At 2-3 amps load, if you allow a mere 30 minutes, the fuse will show obvious heat rise if 2 amps or higher.
.

 

I'm testing it with all the doors and the tailgate closed. I have access to the interior. After the car goes to sleep, you can wake up the MRM using the steering wheel buttons.

I don't have a thermal imaging camera, but I noticed that the entire interior wakes up. I can't figure out how the F32K2 works; it has four RSS wires.


The seat and door buttons don't work. The interior lights and lock buttons in doors work.

 

you have flashed a non-working R-SAM and are dealing with power drain... any idea why F-SAM's is acting up ??
Get both of the SAM to run well then power should get under basic control.

 

Hello there, we try to fix this car togerher
@CaliBenzDriver by saying not working he meant it didn't make any difference
Also as you mention after we disconnect and connect battery it's 20mA and problem is gone, so hard reseting everyting helps.

Now the car seems doesn't go to deeeep sleep, locking and leaving it will go to 50-100mA (keep oscilating) and no lower.
30g keep having +12v all time and when we press button on steering or roof (mrm and dbe on 30g) interior like cluster and radio cd drive wakes up
randomly after couple minutes or hours the interior wake up by itself like on screenshot below and will drain battery to 0
wirings says f32k2 for 30g is controlled by rear sam via RSSsignal(?) with plug at the top of f32 but disconnecting it dont change anything

 

So Long3rsky and Sereq28 are the same team ? Correct ?

Can you guys explain the problem properly and accurately, for one final time.

Yesterday Sereq said K2 relay can go to sleep, but woke up on its own at night.
Today Long said K2 relay will not go to sleep ( turn off ).

Note, I am repeating this again : Whenever engine get turned ON, the K2 relay deep sleep will need 6 hours.
After the 6 hours have passed after engine kill, the deep sleep K2 relay will happen very fast, under 15 minutes after each and every door opening ( wake up ).

So the condition is getting worse today or it was misinformation a few days ago ?

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This is my car.......... door open up to K2 relay off ( deep sleep). Engine been off for more than 1 day.



12 minutes to get it back to DEEP SLEEP at 5 milliamps.


Of which the 5 milliamps is not always 5 milliamps, there is always self-checking happening and can be up to 11 milliamps.





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3.2 amps is easy to find if this is based on a single device/module





Long said : wirings says f32k2 for 30g is controlled by rear sam via RSSsignal(?) with plug at the top of f32 but disconnecting it dont change anything
There is the partial clue in red, above.

That meant the culprit or bad module is powered by Circuit 30 and not Circuit 30g.


====================


Raise your F32 upwards so that you can current clamp all the wires one by one. Its not a fun job due to its very precise wires length.
Since the fuses are inside F32, troublesome to teardown, 3.2 amps load is easily read by any proper DC current clamp.

If you have a good VERY clean 40 amps power supply, you can remove your battery and use the power supply instead, so you have room to work better in battery space for F32 testing.

Below is battery removed from the car. My car is RHD

Above : I was testing the Q-Diode V19


.

My F32, on the left. The right side belongs to a youtuber.





My F32 actual lay out, based on my car. Your diesel version maybe a bit different. But the F32 wiring diag will tell you everything when you read it slowly and carefully.
Current clamp also the wire to the alternator MR8, just in case you have a diode leak at the alternator.




Attached F32 wiring , just in case you do not have it.


=============


I hope you have super sensitive low current clamps like UNI-T 210E or Owon CM2100B, for just in case the 3.2 amps load is not from only 1 module.


Do know the DC current clamp limitation when measuring under 100 milliamps.... when there are ferrous metal around, like in car engine bay.

Read here :
https://mbworld.org/forums/e-class-w...s-awesome.html
and
https://mbworld.org/forums/e-class-w...und-metal.html


Happy troubleshooting......

 

Hello @S-Prihadi, yes we are same team.
First of all thank you for your effort.

I will try clarify all

It seems the car is not going into full sleep mode, it's like 1 step before full sleep with constantly drain between 50-100mA and 30g is alive.
Tonight car was left for 14hrs and at the morning 30g was still active. With 30g active sometimes this 3 amps peaks happens. Sometime after 3hrs, sometime after few days of car standing not touched.
This 3amp doesn't come from one device; I disconnected radio which is powered by 30g and peaks go down to about 2amps - it seems that all 30g devices are woken up for this ~10s period.

As mentioned before after disconnecting and connecting battery without starting the car after few minutes there is audible click of the relay in f32box, 30g is turned off, current drops to ~20mA and car won't drain anymore.
So now we think that some module under 30 doesn't let 30g go off. We will try to find which module it is by measuring currents or trace it on canbus - maybe some module keep spamming the canbus.

 

I see......... so K2 relay could not go to sleep, as latest information.

I looked at my archive.
The K2 relay is a latching type, so you can not disconnect it by simply removing the 4 pins connector.
Once a signal is sent for RELAY ON, it will stay ON and vice versa.

Attached the K2 in use, its data sheet. It is a GRUNER 750H series




==============

I also tested to verify that indeed it is a latching relay.

First the sleep test, approx 12 minutes after door open and closed. K2 will be commanded to be OFF by Rear SAM N10/2.


K2 is still sleeping. 0.2 to 0.6 volts usually as kinda ghost voltage.



I woke up K2 by opening door and close it again immediately.




I disconnected K2 4 pins connector to verify this is a latched type relay. YES IT IS. K2 Stay energized.



I then reconnected the K2 4 pin connector and wait for K2 to go to deep sleep




In approx 12 minutes, K2 went back to deep sleep, as commanded by Rear SAM N10/2. TEST DONE.






===============


Test 2.
K2 in deep sleep mode ( off), shows 0.6 volt.
After this, I will disconnect the K2 4 pin connector and open the door, see what happens


.




I then open-close the left door.



K2 never woke up, because I disconnected the 4 pin connector



However, K2 could never woke up again when I re-connected the 4 pin connector and re-do the door open-close test.
Its on video below :

Yes, I did not test with driver right hand door, to see if K2 will wake up.


---------------------------------

So I used the Ignition Key for reset. I do not use push button start. I am very traditional using KEY FORB INSERT into N73 key slot.
Ignition ON for 2 seconds, engine OFF and I pulley the key fob out.
K2 woke up





21 minutes later I check if K2 went back to sleep within 12 minutes ......NOPE, with key inserted and Igition ON, I recalled the deep sleep will be in 6 hours. Just like ENGINE ON scenario.
I have not check for any DTC yet. Perhaps later or tomorrow.






==============


At Rear SAM N10/2 , there is a POWER AWAKE live data pid. Something like that. I forgot the exact name, but it has "AWAKE" in the description.
Maybe you can check there as to why your K2 never sleep.


I might continue later or tomorrow............................

 

The DTC for the TEST #2 I did........




I could not find the "AWAKE" data PID .......

Try your ON BOARD ELECTRICAL SYSTEM DATA



See which data may help you






7th Dec 2025 at that 12:42PM is at my friend's place.
I did not turn ON stationary heater for sure , but I was testing something something using Xentry for a while.
So Ignition was ON for a while when Xentry being set up. Accidental pressed of the heater ( rear windshield heater ) button ?, maybe, by Xentry thick wire.
This heater has a timer, it is not a dumb switch, it is a soft switch to a module. We can't overheat the heater, the module won't allow. Must be under Rear SAM module.


K2 would be below I guess : NO LOAD CURRENT SHUT OFF. The DTC call it No Load xxxx.

.


Of course K2 is not being shut off when I scan the car.


============

Now, you must first verify if your K2 relay is healthy or not.
Look for ACTUATION or under TEST at Rear SAM for K2, I think it should be available for us to turn ON or OFF the K2 I forgot to check just now...duggh.

 

Problem solved.
This is a rather individual case, so probably no one will encounter it, but I'll describe it anyway.

It was the ECU wiring modified by workshop with knowledge stuck on 90s cars where the car was previously serviced.
We found that 30z 12V power feed was lost on ECU when key is removed. It should be constant power supply from sam-f fuse27.
They (workshop mentioned before) cut this wire at the bottom of sam box and connected to circuit 15 so when we check fuses and voltages on top of sam it was ok.
Also xentry didn't throw and DTC because it's not expecting humans stupidity. We found it only after checking the wiring harness at the ECU itself.

We reconnected 30z as it should be and it turned out that ECU is little broken. After removing the key, the ECU starts going crazy and spamming the signal to relay 87.
To deal with this problem, the only remaining power supply to the ECU was cut off (by workshop mentioned) so it can't switch the relay anymore. This is how they dealt with the problem.

So after removing the key, the ECU was invisible in the vehicle network.
And what the vehicle do before it go sleeps it self checks needed modules (including ECU after ignition).
Again, it's not ready for human stupidity.
In the absence of the ECU, the selfcheck loops until the battery is completely discharged and it happens randomly after minutes or hours of leaving car (weird).
After replacing the ECU with another one (100% working ok) and the correct wiring harness, the car goes into deep sleep mode exactly as you described. After 6 hours and last selfcheck 30g is off and drain drops to average 12mA.





So all the hours spent and cigarettes smoked come down to one wire with diameter of 0.75mm2 / 18AWG.

Happy New Year, goodnight. Have a deep and healthy sleep XDDD

 

Great news
If wiring been "raped", asking car history to previous tech/workshop is a must.
The unique constant power 30Z, only for engine computer it is called 30Z and not the usual 30.