Brake pedal going down (red dash) - SBC low voltage
 

I need help. My W211 (200cdi, 211.004) manufactured 1-2003. Brake pedal going down and dash is red (with beep). Star gives SBC low voltage error and no brak pressuse. Both AGM batterys are new and also alternator is new. We also tested the new SBC units, same problem earlier this summer (I don't remember these codes)... What is problem? Car VIN=WDB2110041A228652.

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How I check this fuse?
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After you saw this screen------what did you do??

I take quick test via Star. Star gives big F --> SBC. Then I go forward to SBC problems --> voltage and then Star gives second and third picture. I did not do anything else yet.

Hey Biff, you are using a great tool and asking how to check a fuse----my advice---- throw the tool in a river, close the hood and visit a proper mechanic!!

Sorry very much. I wanted to kindly ask how to measure the fuse, when I actually found that guideline in WIS. I'm still pretty bad to use the program. Newbie Star user.


And I am very glad if I could get more advice on diagnosing the issue.

Don't let Plutoe disenchant you. He seems to have detailed knowledge of the brand but for some reason chooses to dispense it sparingly and with an air of smug superiority. It's just the way he is. No apparent reason why.
Someone will be along soon who knows what they're talking about and is willing to help.
In the meantime, your owner's manual will show you where the fuse boxes are on the car (there's a few) and you can get down to looking for and checking fuse 73. Just looking at it will tell you if it's blown or not. If a fresh fuse blows right away, quit throwing fuses at it and find out WHY they're blowing.

Plutoe is "keyboard mechanic" on his sober days only.
When I don't even own SD scanner, reading the screen you do have some voltage on the unit. That means that checking fuse might not hurt, but the voltage gets there.
Than statistically talking- those units had recall in USA because bad plug on them.
That would make the plug #1 suspect. Buy a can of MAF, or other electronic cleaner and give the plug good bath.
Next step is check the wiring. I had wires deteriorating on our 10 years old model, so this will be be common problem on those cars.

I just try connect front SAM to SBC via Star --> no connect. Star tell me, that change SBC unit, ground problem or short circuit (code 9033). And second think, I check is there air in brakelines, Star tell me that check had not ok and pressure accumulator 0,5 bar.

What next?

What is your primary language?
Your computer is giving you pretty specific advise.

Sorry my bad language, I'm from Finland =)
Now here is what I mean in english. Is it now better?

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I have seen these errors in the SBC control unit before after swapping SBC units. The problem was the actual connection to the unit itself. The lines were not properly screwed on the SBC unit and where leaking so little that it was not noticeable at first glance. After driving anywhere for about 10-50 mins the car would go into emergency mode and throw codes like those. I would double check the brake lines connected to the top of the unit and make sure they are tight and not cross threaded or such.

Also the only page you should be concerned with in STAR is the control unit SBC as that is what is causing the error message on the cluster. These MBs can have tons of small problems that a normal person just driving it wouldn't even notice ie a undervoltage error or coding error. I have even seen a fault code stored in the IC saying that the reset button was sticking.

If the error is voltage related i have often found that changing the BCM fixes it, assuming all relays and fuses are OK. Those Battery control modules are known to do weird things.

Hope my 2 cents help, this is my first post.

Be sure to check the SBC unit ground wire. There was a recall/service campaign for corrosion on the ground wiring causing errors for certain SBC equipped cars. Search the forums for this issue. Good luck!

Thanks. I have few question...

1. Now my car brake pedal is numb all the time (actually slightly down). The same situation whether the car is running or not. When in push pedel down I heard noise like the rubber is stretched. Behaving brake pedal like this when SBC is broken? Or is there something else wrong?

2. Which all fuses could do this problem?

3. User W211E320, you seen these error before or after swapping SBC unit? After?

4. What is easiest way to check that ground wire working properly?

5. What you think, is it very difficult to test/check SBC if you don't have a Mercedes owe 126-pin socket box and test cable?

6. I want to remember again, that earlier when we testing new SBC unit, pedal going also down and dash was red.

7. My original SBC unit numbers are A 004 431 42 12 (0 265 250 010). I don't see that numbers EPC at all? Why? EPS have just SBC unit numbers: A 005 431 71 12, A 005 431 97 12 and A 008 431 98 12.

When I can't help you with electronic issues, the principal of the brake system is that in normal operation you don't push any piston. The pedal resistance is from the spring who imitate pushing the fluid.
Than when the car switches to emergency mode, the pedal pushes the master cylinder, giving limited braking. That sure can change the noise you hear.
Don't expect too much "hands on experience" in this matter as once the brakes loose the boost, average driver can't tell limited braking from no braking and adrenaline makes the memory going blank. Not too many such failures happen to start with and trying to keep count - you are 6th or 7th driver reporting it on the net in all those years.
W211 in US models has all computers connected to OBD plug and that is the only plug we have.

sometimes you can be a real jerk you know that? if you cant help or choose not to, just stfu and keep your wisdom to yourself. or better yet, take all your wits to your grave, im sure nobody would care.

OP, cant help you with your problem but i hope you find a solution soon. there are some good advices given above, maybe you just have to find somebody who understands the star system better. goodluck mate!

Maybe this will help with more info about the ground-wire issue...

https://mbworld.org/forums/attachmen...005110001f.pdf

I think that that my car have electrical problem... See attachments. When I put key position 2, so dash is always immediately red (red battery icon came first, after that is shows brake problems). Bareke pedal is also soft (going very down, near to floor). Is it ok, that aux battery can't never get over 12,9V (I think that maximum)? Star gives code 9092 togethet code 9071. maybe I have SBC problems, because there is electric problems somehere? SBC unit start randomly, not when open the door (I think it should be). Ant this is very weird problem, sometimes the brakes will work, but then the connection will be lost and the brakes when driving (without warning).

Plaese, help me...

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Engine is running:

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I changed:

- new AGM rear battery
- new AGM aux battery
- K57/2 relay (aux battery)
- brake light switch
- new alternator (Alanko 443201)

Today I test another (same number) BCM unit and almost everythink error codes are gone. Great. Only one error code still stay and this code is C26ED (SBC). Which are the places where I can test circuit 30?

When I put the power on, SBC unit crackles but not start. It is similar to sound like trying to start (starter motor), and the battery is very bad or the bad connection.

What you all expert's think, is it possible that ESP brake control unit not working properly? If any of these units had a problem?

Hello!

I try again another (working properly) SBC unit. I install it and immediately Star diagnostics give me warning like this (sorry finnish language). Warning in english: "Voltage supply (circuit 30) undervoltage. --> Solenoid valve undervoltage 5,6V. --> the battery voltage is too low --> connect the battery charger".

Car working for o moment properly and suddenly (again) pedal going floor and dash is red... When this warning comes, both new batterys was full and batterycharger is was also connected... Help.

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I can't understand. One more I cleaner SBC-unit (third SBC unit) ground wires and then I made brake "airtesting" via Star. Everything was now good and no any errors... Car working ok (200-300kilometers)...

Very weird... =0

What happened next in SBC issue
 

hello
i have read through this thread from the start and have nearly the same issue “Low Voltage” after exchanging standard SL500 for SL55 AMG disc and calipers onto my SL500
Initially I thought my Star was not working correctly
Back brakes have bleed OK have good line pressure
Front have no line pressure
Any ideas please._