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Sensotronic Brake Control
(SBC)
1
R230 and W211: Starting MY2003
327 HO 09 SBC (WJB) 03-05-04
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Objectives At the end of this presentation, you should be able to: 1. Explain the function of and purpose for SBC 2. Describe the customer interface with SBC 3. List the hydraulic and electronic components used for SBC 4. Describe how the “normal” feel of the brake pedal is maintained 5. Explain emergency operation of the SBC braking system 6. Describe “temperature compensation” 7. Explain “Deactivation” and describe when it is necessary to do it 8. “Activate” the SBC system 9. Locate tools and
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Contents Advantages of SBC 5 Driving with SBC 8 SBC components 13 Brake operating unit (BOU) 17 Traction system hydraulic unit 27 Three pressure stages 32 Temperature Compensation 38 Deactivation 39 System activation 42 Bleeding the system 49 3
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SBC Incorporates these Functions: ABS (Anti lock Brakes 1984) + ASR (Automatic Slip Regulation 1991) + ETS (Electronic Traction System 1995) + ESP (Electronic Stability Program 1996) + BAS (Brake Assist System 1998) 4
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Advantages of SBC • Improves metering of required brake pressure – each wheel can be precisely controlled • Improved BAS function – monitors release of accelerator pedal and application of brake – maximum pressure available immediately – pre-filling of system (overcoming play) – when the BAS function is anticipated, slight pressure is applied 5
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Advantages of SBC • Electronic Brake Proportioning: EBP – allows brake proportioning front to back and side to side • No pedal vibration during ABS operation – eliminates “distraction” to the driver during critical moments – indicator light in instrument cluster signals traction loss • Improved driving dynamics: ABS, ASR, and ESP – faster response to brake request inputs 6
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Advantages of SBC • Pressure reduction at standstill – reduces stress on components • Dry braking function – wiper input via CAN – ~every 7 to 14 minutes – brake actuation changes time interval 7
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Driving with SBC - Wake-Up SBC is functional as soon as it is “wakened” by: • opening a door (via CAN) • operating the central locking system (via CAN) • depressing the brake pedal • turning key to position 1 • operating parking brake •The Wake-Up may be followed by a Pre-Drive self Check performed by SBC 8
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Driving with SBC – Pre-Drive Check (PDC) When SBC performs a PDC after a "wake-up", the following are checked: Warning! Pressure is applied to brake calipers (~60 bar) • reservoir pressure (if low, it will be corrected by running the high pressure charge pump in the hydraulic unit) • pressure sensors • control valves • leak tests • operational checks Note: self-tests are constantly conducted during driving (~ once every 16 brake applications) 9
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Driving with SBC – Delayed Off Function Time that SBC remains operational after use: • with vehicle stationary and was locked = 20 seconds • with vehicle stationary and ignition in “0”, brake pedal not operated = 2 minutes • with vehicle stationary, ignition in “0”, brake pedal operated in delayed off phase and released again = 4 minutes 10
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Warning Display Complete ESP control module failure - Instrument cluster will scroll through failure displays 11
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Warning Display SBC control module failure Certain faults will trigger audible signal 12
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SBC Components • Brake Operating Unit (BOU) • Wheel speed sensors • Traction System Hydraulic Unit (A7/3) 13
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W211 System Overview Rear SAM Circuit 30 Brake lights (N10/2) Circuit 87 SBC Circuit 31 SBC CAN ESP control control module (N47/5) Wheel speeds Wheel speed sensors module L6/1, L6/2, L6/3, L6/4 (A7/3n1) Wake up Front Brake lights Stop lamp switch SAM Speed status (S9/1) (N10/1) Diagnostics SBC pedal travel Diagnostic connector sensor (B37/1) (X11/4) 14
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R230 System Overview Circuit 30 Rear SAM Brake lights (N10/8) Circuit 87 Diagnostic connector Circuit 31 SBC (X11/4) control Wheel speed sensors module SBC L6/1, L6/2, L6/3, L6/4 (A7/3n1) CAN ESP control module (N47/5) Wheel Stop lamp switch speeds (S9/1) Wake up Passenger side SBC pedal travel Brake lights SAM (N10/11) sensor (B37/1) Speed status 15
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X11/4 Diagnosis Connection R230 W211 A7/3n1 A7/3n1 SBC SBC X11/4 N47/5 ESP N10/1 L.F.SAM X11/4 Z70/4 N15/5 Pin 9 ESM Z6/33 Pin 9 N47/5 N51/2 ESP ABC 16
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Brake Operating Unit - (BOU) 17
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Brake Operating Unit The Brake Operating Unit (BOU) consists of the following: • Brake fluid reservoir (Do not overfill!) • SBC pedal value sensor • Tandem master cylinder • Brake pressure simulator (Note: no vacuum booster) 18
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Master Cylinder • Fluid level sensor • Fluid return line • Do not overfill • Hydraulic lines to SBC • Supply hose to SBC 19
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Fluid Reservoir Cover • Ultraviolet protection (211 only) 20
