Brief description of components

Dynamic Stability Control (DSC) comprises the following components:

• DSC unit 

  The DSC unit can be broken down into the components of DSC control unit and hydraulic unit.

  The DSC control unit regulates the pressure in the brake system via the hydraulic unit (comprises valve block and pump motor).

• 4 wheel speed sensors 

  Each of the wheel speed sensors registers the speed of an individual wheel. In addition, the wheel speed sensors recognize the direction of rotation (forwards or backwards)

• DSC sensor 

  The DSC sensor measures the rotation of the vehicle around the vertical axis (yaw rate) and the lateral acceleration of the vehicle. A car fitted with Active Steering has two DSC sensors (redundancy). The DSC sensors are connected to the DSC and AS control units via the chassis CAN.

• Steering-angle sensor 

  The steering-angle sensor detects the movements of the steering wheel. The steering-angle sensor is part of the steering column switch cluster (SZL).

  On vehicles with Active Steering, the cumulative steering angle is measured by the cumulative steering angle sensor (= steering angle at steering gear output).

• Internal brake pressure sensor 

  The DSC unit incorporates a brake-pressure sensor. This brake pressure sensor registers the braking pressure applied by the brake pedal and the brake booster.

• 2 additional brake pressure sensors (only in combination with Active Cruise Control, ACC) 

  Two more brake pressure sensors are integrated, one in the front brake circuit and one in the rear brake circuit. A car fitted with Active Cruise Control (ACC) is slowed by DSC when necessary. The braking pressure applied in this way at the front and rear wheels is often very low. It is controlled by means of the brake pressure sensors (objective: to equalize the brake load at the front and rear axles on long downhill stretches).

• 2 brake pad wear sensors 

  The brake pad wear sensors (front left and rear right) monitor the thickness of the brake pads. The Condition Based Service indicator (CBS) in the instrument cluster lights up if brake pad wear progresses to the point at which it becomes critical.

• Brake light switch 

  The brake light switch tells DSC when the brake pedal has been pressed.

• Brake fluid level switch 

  If the brake fluid level is too low, this will be detected and the DSC control unit will be informed.

  An insufficient brake fluid level will be indicated on the instrument cluster by the general brake system warning light (signal via CAN bus).

• DSC button 

  The DSC button is in the center console switch cluster (SZM) The DSC button has three switching states:

  • DSC ready for use
  • DTC ready for use
  • DSC completely switched off

The DSC control unit also communicates with the following control units:

• Digital motor electronics or digital diesel electronics 

  The DME / DDE controls engine adaptation (for example, reduction in engine output to prevent spin at the driven wheels). The DME / DDE also receives the converted wheel speed signal from the rear right wheel. This signal is used to check the plausibility of engine misfires (DME).

• Car Access System or multi-audio system controller/Car Communication Computer 

  The CAS control unit and M-ASK/CCC receive the converted wheel speed signal from the rear left wheel.

  Both these control units use this signal to ascertain whether the car is moving or at a standstill.

• Safety and gateway module 

  The SGM is the gateway between:

  • PT-CAN
  • K-CAN
  • byteflight
  • Diagnostic wire
• Active Cruise Control 

  DSC receives requests from the Active Cruise Control (ACC) via the PT-CAN. In response, DSC reduces speed by applying the brakes at all four wheels.

• Light module 

  As required by law, the brake lights are activated in the event of automatic braking when the Electronically Controlled Deceleration function (ECD) is triggered by the ACC. This function requires a signal sent via the KCAN to the light module (LM).

• Instrument cluster 

  The DSC control unit actuates the indicator and warning lights for DSC in the instrument cluster.

• Electronic gearbox control (vehicles with automatic transmission) 

  The transmission control (EGS) receives the wheel-speed signals via the PT-CAN.

  The gearbox controller responds by adapting the gearshift characteristics for cornering and ascents. In addition, the gearshift characteristics are adapted to winter conditions (high wheel slip).

  Moreover, gearshifts are suppressed during DSC control.

• Central Information Display and Controller 

  The detailed texts for the Check Control messages are shown in the Central Information Display (CID).

  CID and controller are also used to initialize the tire defect indicator (RPA).

• Telephone control unit with GPS antenna 

  If the car is not fitted with a navigation system  , the telephone control unit receives the converted wheel speed signals from the front left and right wheels.

  The telephone control unit uses these signals to pinpoint the car's position as precisely as possible.