Parasitic Drain / Vehicle Control Module?
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Joined: Nov 2022
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Audi Q7
Parasitic Drain / Vehicle Control Module?
Hey y’all, I have a new to me 2017 E43.
If I leave the head unit powered on at shutoff, it will drain the battery down. I have had it with my Indy, who diagnosed the issue as a Vehicle Control Module that needs replacing.
He stated that only a dealer can reprogram / update / replace this module.
The codes the mechanic observed had to do with the car’s WiFi connectivity. Essentially it can’t connect to the MB mobile WiFi that makes MBrace work, so the car keeps walking to try. I observe that the car says SOS NOT READY in the top right of the infotainment screen. Seems like all this checks out.
Has anyone else had the same experience?
I’ve just got the car back and as dumb as it sounds, I have turned off WiFi Updates and turned off WiFi in Connectivity. Will update if that does me any good.
is there a fuse I can pull related to the car’s connectivity features?
If I leave the head unit powered on at shutoff, it will drain the battery down. I have had it with my Indy, who diagnosed the issue as a Vehicle Control Module that needs replacing.
He stated that only a dealer can reprogram / update / replace this module.
The codes the mechanic observed had to do with the car’s WiFi connectivity. Essentially it can’t connect to the MB mobile WiFi that makes MBrace work, so the car keeps walking to try. I observe that the car says SOS NOT READY in the top right of the infotainment screen. Seems like all this checks out.
Has anyone else had the same experience?
I’ve just got the car back and as dumb as it sounds, I have turned off WiFi Updates and turned off WiFi in Connectivity. Will update if that does me any good.
is there a fuse I can pull related to the car’s connectivity features?
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Joined: Jun 2012
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From: Toronto
2022 E53 AMG
Turn it off is good since Mercedes already advise that they will end the services as technology moves forward. MBrace is at it's end of life as MercedeMe is the newer app but that it also being warned that it's going to be at it's end of life in the future.
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Audi Q7
Additional note on issue
Documenting for anyone else having similar issue; I remembered some comments from my mechanic after my initial post:
- the car sat for about 36 hours before his guy got to it and it fired up in spite of the battery warning so not draining as severely as I thought (with the head unit powered off at shut down)
- after updating the battery management system, he observed the car waking and drawing power when it should not have been but it did not drain to a critical level
He concluded that the car is throwing the “12V Battery Start Engine” error after the car does its own sleep/wake cycle whether or not the battery has suffered significant drain.
A behavior I forgot to document in my original post is that oftentimes, when I start the car the head unit powers up after being manually powered down, which it should not. This is in line with something in COMAND powering up when it should not.
I also observed that the massage seats were inoperable when I got the car but after whatever code resets and updates the Indy did, now they work, so…..small victory.
- the car sat for about 36 hours before his guy got to it and it fired up in spite of the battery warning so not draining as severely as I thought (with the head unit powered off at shut down)
- after updating the battery management system, he observed the car waking and drawing power when it should not have been but it did not drain to a critical level
He concluded that the car is throwing the “12V Battery Start Engine” error after the car does its own sleep/wake cycle whether or not the battery has suffered significant drain.
A behavior I forgot to document in my original post is that oftentimes, when I start the car the head unit powers up after being manually powered down, which it should not. This is in line with something in COMAND powering up when it should not.
I also observed that the massage seats were inoperable when I got the car but after whatever code resets and updates the Indy did, now they work, so…..small victory.
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Joined: Nov 2022
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Audi Q7
Issue resolved
Resolved my issue and closing the loop for others with this reply. There is a chance others experience something similar with MBrace sunset in 2026.
My codes, self walking and battery drain were related to WiFi connectivity. The car was seeking a network that not longer existed. The dealer deleted/deactivated the Hermes LTE communication module and those issues resolved. They needed to ask MB for permission to do this.
They also observed the battery losing voltage and recommended replacing it - I installed a new battery as soon as I got the car hoping that would solve the issue and it seems that battery was defective.
It’s possible that the underlying issues would have been masked for a while if I’d received a functioning battery when I first started troubleshooting.
Other quirky behaviors were related to consistent low voltage / losing voltage and have been resolved with the updates and new battery.
All in cost to me was 1 hour of dealer labor for programming and an AGM battery. A different dealer could try to squeeze more hours out of your visit.
Footnote: the dealer also did a Recall that involved updating the ECU and the driving performance, especially transmission behavior, is markedly improved. Worth it for any owners who’ve been putting it off or were unaware - I believe it was just issued early in 2025.
My codes, self walking and battery drain were related to WiFi connectivity. The car was seeking a network that not longer existed. The dealer deleted/deactivated the Hermes LTE communication module and those issues resolved. They needed to ask MB for permission to do this.
They also observed the battery losing voltage and recommended replacing it - I installed a new battery as soon as I got the car hoping that would solve the issue and it seems that battery was defective.
It’s possible that the underlying issues would have been masked for a while if I’d received a functioning battery when I first started troubleshooting.
Other quirky behaviors were related to consistent low voltage / losing voltage and have been resolved with the updates and new battery.
All in cost to me was 1 hour of dealer labor for programming and an AGM battery. A different dealer could try to squeeze more hours out of your visit.
Footnote: the dealer also did a Recall that involved updating the ECU and the driving performance, especially transmission behavior, is markedly improved. Worth it for any owners who’ve been putting it off or were unaware - I believe it was just issued early in 2025.
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Audi Q7
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