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

[jacka]

I need help. My W211 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?





How I check this fuse?

 

[jacka]

W211 is 200cdi (211.004) and VIN=WDB2110041A228652.

 

[grober]

Welcome to the W211 E- Class!

FS2 is the front pre-fuse unit.

 

[jacka]

Welcome to the W211 E- Class!

FS2 is the front pre-fuse unit.

How I know is it ok or not? That fuse don't look like usual fuse.

 

[grober]

Its basically a power bus unit with one big power inlet and several oulets via fused links. You need to locate the f73 outlet connector and check its voltage . While sometimes these links can be replaced individually Mercedes seem to prefer to replace the entire assembly.

Internals may be something like this but this stuff is poorly documented!

 

[jacka]

Thanks. Upper picture, how I see is fuses ok without opening the box? F32f72 and F32f73 are the left side ones. Is there metal fuses inside. And who sell these fuses?

 

[merc85]

Some very good info there! Thankyou

 

[jacka]

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.

 

[grober]

Can't answer that except to say that your orginal sbc unit part no has been susperceded. Usually Mercedes chose to detail the old part no in their EPC as "replaced by" with the new part no but not in this case evidently. Another thread advises using the Bosch number as a link to the new part and says it may be sourced and fitted via a Bosch service centre as an alternative to Mercedes. W211 ''Service Brake - Visit Workshop!" [Archive] - Mercedes-Benz Owners' Forums
Basically these pumps were programmed for a fixed number of operations after which they had to be replaced. After many failures Mercedes and Bosch allowed the unit to be reprogrammed once to extend its working life rather than replaced. Unfortunately this opened the door to many second hand "reprogrammed" units with limited hours left--- to be sold as good secondhand operational units. The only way to guarrantee a bona fide unit is to get your existing one checked out and possibly replaced by a bona fide MERCEDES DEALER/SPECIALIST or Bosch service centre.
I'm afraid I can shed no light on a source for the fusable links if Mercedes don't supply them.

 

[jacka]

I just take off SBC unit and I want to check carbon brushes? Which are right carbon brushes measurement if old ones are bad shape? 5x5x15 millimeters?

 

[AMGeed]

I just take off SBC unit and I want to check carbon brushes? Which are right carbon brushes measurement if old ones are bad shape? 5x5x15 millimeters?

If you don't know what you are doing, I'd be very wary of messing about with the pump The SBC braking system is a complex piece of engineering and should be left to the experts to fix IMHO.

 

[Auto-mobile]

As above, I am aware of someone who "rebuilt" his own pump and it didn't end well.

 

[jacka]

SBC unit carbon brushes was ok. I check again errors via Star. There is "normal" SBC EPS error and BCM, Is this BCM the problem? BCM have very old (original? softwere)? And colud someone tell me which are connectors 2?

 

[grober]

Welcome to the W211 E- Class!

Try the electronics-battery section. Its obvious that the SBC system is flagging up certain low voltages - the reasons for this can simply be faulty earth connections or far more complex problems. Has the auxilliary battery ever been renewed? One of its main purposes is as a SHORT TERM backup for the SBC SYSTEM should the overall main battery/alternator fail to supply the SBC system with adequate voltage. Star is flagging up a low voltage supply situation but the causes for this may not be as straightforward as the fault messages indicate.

 

[b1g1an]

From memory there are a lot of reported problems down to the wires under the aux battery becoming frayed.

 

[jacka]

Welcome to the W211 E- Class!

Try the electronics-battery section. Its obvious that the SBC system is flagging up certain low voltages - the reasons for this can simply be faulty earth connections or far more complex problems. Has the auxilliary battery ever been renewed? One of its main purposes is as a SHORT TERM backup for the SBC SYSTEM should the overall main battery/alternator fail to supply the SBC system with adequate voltage. Star is flagging up a low voltage supply situation but the causes for this may not be as straightforward as the fault messages indicate.

Thanks. Couls you tell me all these car ground/earth places, what I have to check? Someone write that, that W211 have electric/wire problems under aux battery. Do you ever heard like these?

 

[grober]

THE SBC EARTH POINT is located on the inner wing beside the unit. I havn't heard about the wiring issue but you would need to locate the aux battery to remove it and inspect the wiring underneath??

 

[jacka]

THE SBC EARTH POINT is located on the inner wing beside the unit. I havn't heard about the wiring issue but you would need to locate the aux battery to remove it and inspect the wiring underneath??

I check today under aux battery, Everythink look ok... And I also check SBc ground. Where is BCM unit ground/earth and is there where can be corrosion?

 

[jacka]

I check today under aux battery, Everythink look ok... And I also check SBc ground. Where is BCM unit ground/earth and is there where can be corrosion?

I found this, check this link. Is that pins 7 include that wire bundle?
Same problems like my car...

Where can i find the k57/2 relay for the aux battery?

 

[grober]

I check today under aux battery, Everythink look ok... And I also check SBc ground. Where is BCM unit ground/earth and is there where can be corrosion?

See the last link on the W211 I posted Welcome to the W211 E- Class! electrical battery section The BCM location is pictured there. Unlikely to be an earth problem there.