Dynamic Stability Control Mk60E5

34 01 04 (107)
Dynamic Stability Control Mk60E5
E85, E86, E87, E90, E91, E92, E93





Introduction
BMW 3-Series vehicles with 6-cylinder engine are equipped as standard with Dynamic Stability Control Mk60E5. This version is an advanced development of DSC Mk60E used on the E87. On the DSC Mk60E in the E87, the brake pressure sensor was integrated in the DSC unit (compared to the DSC Mk60).
The DSC Mk60E is also fitted on E90/E91 vehicles with 4-cylinder engine.
The supplier for both DSC Mk60E and DSC Mk60E5: Continental Teves.

Further launch dates for DSC Mk60E5:
- From 09/2005 in the E87, only on vehicles with 6-cylinder engine
- From 01/2006 in the E85
- From 04/2006 in the E86

> - E85, E86 [system overview ...]
> - E87, E90, E91, E92, E93 [system overview ...]

Note: Vehicles with all-wheel drive (E90, E91, E92)
These vehicles are equipped as standard with DSC 8Plus.

[for further information, please refer to SI Technology (SBT) 34 01 05 126] Dynamic Stability Control 8Plus

New features of the DSC Mk60E5:
- > E92 from 06/2006 and
> E90, E91 from 09/2006 and
> E93 from 12/2006:
The LDM control unit is no longer fitted on vehicles with option 544 "Cruise control with brake function". Because of a software modification in the DSC control unit (DSC Mk60E5), the DSC control unit assumes control of the functions of the LDM control unit. LDM = "longitudinal dynamics management"
- Solenoid valves with variable map for flow rate:
so-called "analogised" solenoid valves (distribution valves and inlet valves)
- 5 brake pressure sensors integrated in the new DSC unit
- 4 active wheel-speed sensors with wheel direction recognition (only E87 with 6-cylinder engine, E90, E91, E92, E93)
- 1 longitudinal-acceleration sensor on the board of the DSC control unit
> E85, E86: the longitudinal-acceleration sensor is integrated in the DSC sensor.
- DSC sensor taken from the E87, with redundant signals on vehicles with Active Steering (2x rate of yaw, 2x lateral acceleration)
- Additional functions of DSC
DSC is a driving stabilisation system. DSC has the following tasks/advantages:
- DSC optimises driving stability when puling away, accelerating and braking, and when coasting.
- DSC recognises and reduces unstable driving conditions such as understeering or oversteering.
- DSC improves traction (especially with DTC: Dynamic Traction Control)
Within the limitations of the laws of physics, DSC helps to keep the vehicle on a safe course.
To do this, DSC must know the following parameters of driving dynamics:
- Yaw rate as a measure of rotary movement of the vehicle around the vertical axis
- Lateral acceleration
- Road speed
- Longitudinal acceleration
In addition, the driver's intentions are recognised from the following factors: Steering angle, brake pressure and throttle setting, which the driver sets via the accelerator pedal. These values are used top calculate an actual condition in which the vehicle is currently moving. The actual condition is compared to the value calculated by the DSC control unit. If the actual value differs from the calculated value, DSC is activated and initiates brake actions and/or engine control functions.
Advantages:
DSC counters all dynamically unstable driving conditions. This means DSC brings about maximum active safety within the physical limits. DSC thus enhances driving comfort by allowing more relaxed driving.

Brief description of components
The following components are described for the Dynamic Stability Control (DSC):

- Inlet valves and distribution valves
These solenoid valves used to be digitally actuated: either OPEN or CLOSED.
The inlet valves for the wheel brakes and distribution valves are actuated in such a way that the flow rate is variably controlled. Because these solenoid valves work like analogue solenoid valves, they are known as "analogised" solenoid valves.
The analogised solenoid valves allow DSC to realise additional functions.

- 4 active wheel-speed sensors
> E87 with 6-cylinder engine, E90, E91, E92, E93
The active wheel-speed sensors measure the speed of the individual wheels. This type of sensor also recognises the direction of rotation of the wheels.

- DSC sensor
The DSC sensor measures the rotation of the vehicle around the vertical axis (yaw rate) and the lateral acceleration of the vehicle.
> E85, E86
The longitudinal-acceleration sensor is part of the DSC sensor.
On vehicles with Active Steering, a DSC sensor is installed with redundant sensor system (i.e.. 2 signals for yaw rate and 2 signals for lateral acceleration).

- DSC unit
The DSC unit consists of the hydraulic unit and the DSC control unit.
All 5 brake pressure sensors are integrated into the valve block of the DSC unit.
The board of the DSC control unit also holds a longitudinal-acceleration sensor.
> E85, E86
The longitudinal-acceleration sensor is not part of the DSC unit but rather part of the DSC sensor.

- Steering-angle sensor
> E85, E86
The steering-angle sensor uses sliding contacts to measure the angle of rotation of the steering wheel.

>E87, E90, E91, E92, E93
The steering-angle sensor optically measures the angle of rotation of the steering wheel.

- DTC button
> E85, E86
The DTC button is located in the SZM (centre console switch cluster).
>E87, E90, E91, E92, E93
The DTC button is located in the centre console between the central air vents.
The DTC button has 3 switching states:
1. DSC operational (standard setting)
2. DTC operational
3. DSC and DTC completely deactivated
Additional input signals from the following components:
- Brake-fluid-level switch
If the brake fluid level is too low, this will be detected (via a reed contact in the expansion tank) and an appropriate message sent to the DSC control unit.
DSC is deactivated if there is insufficient brake fluid. There would otherwise be a risk of air being drawn into the brake system.
- Brake light switch
Together with the signals from the brake pressure sensors, braking actions are recognised.
- Parking brake warning switch
DSC will recognise skidding that has been deliberately initiated by the driver. Regulation will not take place. Reason: a handbrake turn should remain technically possible.

DSC system functions
DSC uses brake actions and engine intervention to influence longitudinal and lateral dynamics.
DSC comprises numerous functions.

Functions familiar from current DSC:
- ABS: Anti-lock braking system
- EBV: Electronic brake force distribution
- CBC: Cornering Brake Control
- ASC: Automatic stability control
- DTC: Dynamic traction control
- MSR: Engine drag torque control
- DBC: Dynamic brake control
- RPA: Run Flat Indicator (not a driving dynamic control function)
- CBS: Condition Based Service (not a driving dynamic control function)
New functions for DSC Mk60E5:
- Brake Standby through pre-tensioning of the brakes in an emergency
- Brake disc drying on wet roads
- Fading compensation
- Soft stop when braking to standstill (only E87 with 6-cylinder engine, E90, E91, E92, E93)
- Start-off assistant
- Adapted interface for cruise control with brake function (only E90, E91, E92, E93)
- Adapted interface for active cruise control (only E90, E91, E92, E93)
- Yaw-moment compensation via active steering (only E87 with 6-cylinder engine, E90, E91, E92, E93)



ABS: Anti-lock braking system
ABS prevents the wheels from locking when the brakes are applied.
Advantage: Optimum utilisation of road surface friction - the vehicle remains stable and steerable.
Brake pressure is regulated at all wheels to ensure that each wheel runs with optimum slip.
When this happens, slip is controlled so that the maximum possible braking and lateral stability forces can be transmitted.



EBV: Electronic brake force distribution
EBV is a component of ABS and controls the brake force distribution between the front and rear wheels.
Advantage: Regardless of the load state of the vehicle, the best possible braking distance is achieved while driving stability is maintained.
Modern vehicles have relatively large brakes on the rear axle to shorten braking distances. To prevent the rear wheels from being overbraked in certain driving situations, EBV permanently monitors slip. EBV controls rear axle slip in dependence of the front axle.



CBC: Cornering Brake Control
CBC is an extension of ABS. CBC enhances driving stability if the brakes are applied when cornering.
Advantage: If the brakes are applied in a corner, optimum brake force distribution ensures optimum tracking stability.
When cornering, even very light braking can shift the axle-load distribution to the left or right so that driving stability is impaired. If required, CBC generates a stabilising load moment when the brakes are applied lightly outside the ABS intervention range.



ASC: Automatic stability control
ASC prevents the wheels from spinning when the vehicle is accelerating.
Advantage: Improved traction. The vehicle remains stable.
If one of the wheels of the drive axle is on a high-grip surface and the other is on a slippery surface, the wheel tending to skid is braked.
ASC also intervenes in the engine control (to reduce the ignition angle, injection quantity, throttle valve setting).



DTC: Dynamic traction control
DTC is a version of DSC that has been optimised for forward momentum in certain road conditions. Dynamic traction control (DTC) offers better traction as a trade-off against a reduction in stability in some circumstances. Consequently, its use should be reserved for exceptional conditions. It is advisable to briefly activate DTC in the following exceptional circumstances:
- To rock the vehicle free or pull away in deep snow or on a loose surface.
- When driving on snowy uphill stretches, in slush and on roads that have not been cleared.
- When driving with snow chains.
The DTC function approximates to that of DSC with a slightly modified control strategy.
DTC can be activated by deactivating DSC (DTC button). DTC intervenes in the braking actions to imitate the function of a conventional differential lock. This effect of this is to increase the input torque on those wheels that are on a higher-friction surface.
Advantage: Higher traction is available with DTC.
Vehicle stabilisation intervention (e.g. reduced power output) is made slightly later than with DSC. In certain situation, the driver has to intervene more intensively himself to stabilise the vehicle.



MSR: Engine drag torque control
The drive wheels are able to lock if a lower gear is selected of load is abruptly changed on a slippery road surface.
Engine drag torque control provides protection against locking drive wheels.
Advantage: The drive wheels retain their lateral stability in overrun mode.
The wheel speed sensors tell MSR as soon as the wheels are about to lock. MSR then briefly reduces the engine's drag torque by opening the throttle slightly.



DBC: Dynamic brake control
DBC supports the driver in emergency braking situations. It does this by automatically increasing braking pressure when the brake pedal is not depressed with sufficient force.
Advantage: Shortest possible braking distances in emergency braking situations by achieving ABS regulation on all four wheels.
The brake pedal is frequently not depressed strongly enough in emergency braking situations. The ABS feedback control range is not reached (or not on all 4 wheels).

The return pump increases the brake pressure until ABS regulation is activated:
- If the brake pedal is depressed quickly with insufficient pedal pressure (recognised from the signal from the brake pressure sensors)
- If the brake pedal is depressed slowly and then with greater braking deceleration than necessary (recognised from the signal from the brake pressure sensors), when both front wheels have reached the ABS control threshold.
Example of a typical situation:
The traffic slows, making light braking necessary at first, but then demands as short a stopping distance as possible.



RPA: Run Flat Indicator
RPA is not a driving dynamic function.
DSC uses the Run Flat Indicator (RPA) to monitor the tyre pressure throughout the journey.
The RPA records the wheel speeds using the wheel-speed sensors of the Dynamic Stability Control (DSC). The RPA compares the speeds of the individual wheels with the average speed. In this way the RPA is able to detect a loss of tyre pressure.
The RPA detects a drop in pressure below about 30 % ± 10 % of the initial value. The RPA indicator and warning light indicates a drop in tyre pressure.
The RPA will indicate this after just a short distance, as a rule after a few minutes, from a certain minimum speed (e.g. 25 km/h) up to the permissible top speed.
Initialisation is started manually. Then (after a journey has started), initialisation runs automatically. In other words, the circumference of individual tyres are recorded and evaluated.

The initialisation phase lasts approx. 5 to 15 minutes for the individual speed ranges.
[for further information, please refer to SI Technology (SBT) 36 01 04 078]



CBS: Condition Based Service
CBS is not a driving dynamic function.
Condition Based Service, as the name suggests, is a means of ensuring that the car is serviced as and when necessary. CBS comprises various maintenance operations, e.g. engine oil and brake pads.
The remaining distance for the front and back brake pads are calculated separately in the DSC control unit.
When making the calculation, the condition of the brake pad wear sensors is taken into account (reference point at 6 mm and 4 mm).
[for further information, please refer to SI Technology (SBT) 00 01 04 070] Condition Based Service (CBS)

New functions for DSC Mk60E5



Brake Standby through pre-tensioning of the brakes in an emergency
Pre-tensioning the brakes shortens the brakes' response time.
If the accelerator pedal is rapidly released (accelerator pedal angle), the brakes are immediately pretensioned. DSC generates a low braking pressure through the "analogised" solenoid valves, without creating any measurable deceleration of the vehicle. The working clearance between the brake pads and brake disks is equalised. If the brakes are not applied within a certain time, this preliminary brake pressure is cancelled. The early pre-tensioning of the brake pads is active at road speeds greater than 70 km/h.



Brake disc drying on wet roads
Braking dry removes moisture that gathers on the brake discs during journeys on wet roads or in rain. The brake pads are lightly applied. This function also shortens the brakes' response time.
Depending on the signal from the rain sensor and the position of the wiper switch, DSC cyclically generates a low brake pressure. This creates no measurable deceleration on the vehicle. The brake pads are cyclically applied. This means that the brake disc are regularly wiped down. How often and how long the brake pads are applied depends on:
- The intensity of the rain, e.g. the speed of the windscreen wiper
- Road speed greater than 70 km/h



Fading compensation
Fading means: braking effect deteriorates as a result of high brake-disc temperatures.
If fading is detected, DSC reacts by increasing the brake pressure above that specified by the driver.
At very high brake-disc temperatures, fading compensation is indicated by the following:
- General brake warning lamp lighting up yellow
- Check-Control symbol in LCD display in instrument cluster lighting up yellow
DSC detects fading as follows: DSC compares the current vehicle deceleration with a nominal value based on the current brake pressure. DSC increases brake pressure until the nominal deceleration is achieved or until all wheels are subject to ABS control. The process is ended when the brake pedal is no longer depressed or when the speed drops below a certain threshold.



Soft stop when braking to standstill (only E87 with 6-cylinder engine, E90, E91, E92, E93)
Soft stop prevents the vehicle from jolting to a stop (e.g. with an inexperienced driver).
When the vehicle is braked to a standstill, there is no uncomfortable jerk (causing the occupants to "lurch" forward). DSC calculates the moment that standstill can be expected from the current road speed and deceleration.
Just before standstill is achieved, the brake pressure on the rear axle is reduced so that the vehicle stops with practically no jerking. Soft stop is only active for light braking, so that the shortest possible stopping distance can still be achieved in emergency braking situations.



Start-off assistant
The start-off assistant prevents the vehicle from moving unexpectedly when the driver moves his foot from the brake pedal to the accelerator pedal (e.g. when pulling away on a hill):
- uphill in forward gear
- uphill in reverse gear
It does this by maintaining the brake pressure needed to hold the vehicle.
The gradient is recorded by the longitudinal-acceleration sensor in the DSC control unit. From the gradient, the necessary braking torque or engine torque is calculated. When pulling away is detected, brake pressure is reduced as soon as the available engine torque is sufficient to move the vehicle in the direction required. The start-off assistant is deactivated when the parking brake is applied. If no move is made to pull away within 2 seconds of the brake pedal being released, the start-off assistant will be deactivated.



Adapted interface for option 544 "Cruise control with brake function"
> E92 from 06/2006 and
> E90, E91 from 09/2006 (up to 09/2006: "cruise control with brake function" always with LDM) and
> E93 from 12/2006
The LDM control unit is no longer fitted on vehicles with option 544 "Cruise control with brake function". Because of a software modification in the DSC control unit (DSC Mk60E5), the DSC control unit assumes control of the functions of the LDM control unit. LDM = "longitudinal dynamics management"
[For further information, please refer to SI Technology (SBT) 66 03 04 086] Description and Operation



Adapted interface for option 541 "active cruise control"
> E90, E91, E92, E93 ("active cruise control" always with LDM)
The interface between Dynamic Stability Control (DSC) and active cruise control (ACC) has been adapted with the longitudinal dynamic management system. The software in the DSC control unit evaluates the demands of the ACC even more quickly. Pressure at the wheel brakes can be built up or reduced more efficiently from the point of view of vehicle deceleration and comfort.
The longitudinal dynamic management (LDM control unit) transmits the signals from the active cruise control. Part of the ACC software is integrated in the LDM control unit.
[for further information, please refer to SI Technology (SBT) 66 03 04 086] Description and Operation



Yaw-moment compensation via Active Steering
> E87 with 6-cylinder engine, E90, E91, E92, E93
Active Steering offers an additional function for driving stabilisation:
With conventional systems, the driver has to actively steer the vehicle in a straight line if the brakes are applied on a road surface with non-uniform traction levels ("m-split"). Countersteering keeps the vehicle in its track and helps to achieve acceptable braking distances.
For such situations, Active Steering actuates these active steering actions. The vehicle is stabilised. At the same time, a shorter braking distance is achieved.
The DSC control unit calculates the yaw rate with the brake pressure sensors on the front axle.
The DSC control unit transmits to the Active Steering control unit the yaw-moment compensation correction angle needed for stabilisation.

Preconditions for activation
DSC is activated after every engine start.

Notes for service staff
Service staff should note the following points:

- General information:
- Diagnosis:
- Encoding/programming:

Subject to change.