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I recently got the nonstop beeping, all bold, red "BRAKE" message in the cluster and the brake pedal went to the floor, and there was little to no braking. Luckily, I was in the drive way and not on the road when this happened. I turned it off and back on and it went away for a few seconds, but then the issue would return. So I parked it and did some research and read somewhere that this can happen if the accessory battery is not fully charged. So I left it on the trickle charger for a day or two, starting it periodically, and letting it run for about 5 mins or so. This happened about a week ago and the brakes seem to be working fine now, although I've only driven down the block a few times at no more than 30 mph. But they pull straight and STRONG. Now the message on the cluster now says BRAKE, Brake Service Required. So does anyone know if this a message as a result of the accessory battery going flat, or is it a true indicator of the brakes needing servicing? I think the SBC unit (which was recently replaced via extended warranty) may have gotten confused when it was not getting full power, and now it thinks the brake pedal threshold has been reached. But that's just a guess. I've had this car for 4 years or so and I've never had any other brake issues. I only drive the car about 4 times a month, and nothing spirited. Just a 40 mile round trip to work and back, 3 or 4 times a month. I hesitate to take it to the dealership as I know they're gonna charge the crap out of me no matter what. Also, does anyone know if it's safe to drive the car, or would that be ill-advised? But any added information or insights on this issue will be greatly appreciated.
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Need to get a code reader hooked up to the car to see exactly what's being reported.
It's well worth it to buy at least a basic code reader. Even if you're not a DIYer, you can at least be armed with accurate information before taking it into a shop.
I think the SBC unit (which was recently replaced via extended warranty) may have gotten confused when it was not getting full power, and now it thinks the brake pedal threshold has been reached.
How recently was the SBC unit replaced?
If within a reasonable interval (and especially still within the SBC extended warranty period), the dealership shouldn't charge you to diagnose what appears to be a brake system issue post-replacement.
Regarding the accessory battery, recharging it isn't enough to verify its health. You need to load test it to determine that.
Amazon has some good BF sales going. You can pick up a Foxwell scanner with the MB software and any well-rated battery tester to get things moving towards a resolution.
Great pictures! Definitely forget about the benz dealership, they are robbers and liars. Sure there are two percent of them that are honest, but good luck finding one of those. Need to have an indy shop with guys who know these cars and are actually honest. I had an alternator that the previous owner installed, that went bad and began putting out 30 Volts instead of 12-14. First system on the car to notice this condition was the SBC and it immediately gave warnings and threw a fit. If the SBC isn't happy, the car will not be stopping well at all, and can't be driven. I was pretty sure the SBC had quit due to its own fault, My trusted indy shop figured out it was the alternator. A cheap Duralast brand unit from Autozone was on the car! Never buy cheap junk parts for these cars. Had it been the SBC, Mercedes warranty would have replaced it. Your issue could still be the trunk battery. How old is it? Have it load tested. Replacement cost of that battery under $250. A good code reader probably will give you some more insight too.
I'm in the middle of relocating cross country and (like a dumb @$$) I left my Autel scanner at home, and it won't be here for another month. But I would agree that the problem probably stems from a not fully charged battery. I've had the car for 4 years and have never replaced it, so gonna take it out and have it load tested today. Also gonna take it to a local shop that my cousin swears by and see what they say. But thanks for the responses!
You can run the car without the rear battery installed so your brake issue is not connected to that.
There is a serious issue with the brake system, probably the SBC controller. Even with this module disconnected you will still have unassisted front braking through the 'last line of defence' backup hydraulic circuit, so the pedal going to the floor is a worry.
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