Active Brake Assist Limited and Parking Brake Messages
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Joined: Jul 2007
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From: Memphis, TN
Active Brake Assist Limited and Parking Brake Messages
I recently started to get these two messages on startup. It was not frequent a week ago and now I get the errors everytime. I have cleaned the sensors but it does not clear the errors. I turned the active brake assist off in the MBUX now no errors but I don't want to drive without this feature. Any other EQS owners seen this error before?
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Joined: Oct 2023
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24 EQS 580 4matic sedan Pinnacle trim w/Exec. rear seating pkg.
I recently started to get these two messages on startup. It was not frequent a week ago and now I get the errors everytime. I have cleaned the sensors but it does not clear the errors. I turned the active brake assist off in the MBUX now no errors but I don't want to drive without this feature. Any other EQS owners seen this error before?
@gamoon ,
That's a frustrating set of errors, especially when they become persistent. Your first instinct to clean the external sensors was a good, logical first step.
However, based on my experience with these platforms, the fact that you are getting two seemingly unrelated system errors simultaneously on startup points away from a simple dirty radar sensor or camera. This is likely not a sensor issue at all, but rather a systemic one.
Here is my analysis of the most likely culprit.
The Unseen Cause: A Failing 12V Battery
In modern, computer-intensive vehicles like the EQS, the single most common cause for multiple, unrelated system errors appearing at startup is a weak or failing 12V battery.- The "Why": When you start the car, dozens of individual computers (ECUs) that control everything from your brakes to your parking sensors have to boot up simultaneously. This process requires a stable, consistent voltage from the 12V battery. If the battery is aging and can't provide that stable voltage during the boot-up sequence, some modules will fail their initial self-check. They then report a "limited" or "inoperative" status to the main system, triggering the warnings you see.
- The Pattern: This perfectly explains why you see both an "Active Brake Assist" and a "Parking Brake" error. It's not that both systems have failed; it's that the underlying power system they rely on is momentarily unstable when the car wakes up.
Your Action Plan
You are right to be concerned about driving without these features active. Disabling the systems is a temporary workaround, not a solution. My strong recommendation is a dealership visit.However, to ensure you are taken seriously and the process is efficient, I would approach it like this:
- When you speak to your Service Advisor, don't just report the error messages.
- State clearly that you have "multiple, unrelated system warnings that appear simultaneously on startup."
- Then, state that based on your research, you suspect a "systemic voltage issue, likely originating from a weak 12V battery," and that you would like them to test the 12V battery's health and the charging system first, before attempting any complex software flashes or sensor replacements.
Hope this deeper analysis helps you get a swift and accurate resolution.
