Does this Stop the Car?

March 17, 2014 | Reply More

First, we got anti-lock brakes, controlling wheel speed while decelerating. This evolved into traction control, controlling wheel speed under acceleration. Now we have advanced versions of Dynamic Stability Control. BMW drivers are safer than ever before, but how do we keep this winning streak going?

DSC has become more integrated since this early version.

DSC has become more integrated since this early version.

When drivers enter a BMW vehicle, they have a certain expectations. They expect lively acceleration along with a smooth idle. They expect a taut suspension, but not one so stiff it’s jarring. They expect the car to “ride on rails” through a corner even with road irregularities. Over the years, BMW has built its sporty reputation on engine performance and precise handling.

When replacing a wheel speed sensor, it is important to route the wiring as you found it in its various holding clips on the strut and in the connector housing. You don’t want the sensor wiring tugging on the sensor or the connector because eventually it will fail.

When replacing a wheel speed sensor, it is important to route the wiring as you found it in its various holding clips on the strut and in the connector housing. You don’t want the sensor wiring tugging on the sensor or the connector because eventually it will fail.

Later model BMW suspension systems are integrated with anti-lock brake and traction control systems to form Dynamic Stability Control (DSC). The electronic control units involved share information about the car’s rate of acceleration or deceleration, body roll in a corner, and individual wheel speeds. Although DSC has been with us for a while now, many technicians do not realize the extensive developments that have occurred on the software side of DSC. These features help reduce braking distances by anticipating the driver’s needs and taking into account environmental conditions from information on the CAN. Also, most drivers do not realize everything that is involved — they only notice when it does not work.

Most complaints will have to do with a DCS warning light, although some customers may notice that they no longer have a speedometer reading, or that the vehicle isn’t shifting properly. You may not think of querying the DSC unit right away unless you already know that it acts as the vehicle speed sensor for the entire car. The signal is picked up by the wheel speed sensors and passed on through the CAN. For example, on the E46 chassis with DSC III the left rear speed sensor signal is processed and transferred on the CAN bus to the MK III (navigation) and IKE (instrument cluster) systems. The navigation system compares GPS location to vehicle mileage and comes up with a more accurate reading of location. The instrument cluster uses this data to operate the speedometer. The right rear speed sensor signal is process and passed on to the DME (Digital Motor Electronics) and is shared by the AGS (Automatic Gearbox System) to control shifting.

Where Do I Start?

The DSC control unit is serviceable separately from the hydraulic unit. The new one will be in “factory” mode for shipment. You will need to use your iComm/ISTA/P to code it to the specific car. With a paid subscription to www.bmwtechinfo.com, you can access this software and program the module.

The DSC control unit is serviceable separately from the hydraulic unit. The new one will be in “factory” mode for shipment. You will need to use your iComm/ISTA/P to code it to the specific car. With a paid subscription to www.bmwtechinfo.com, you can access this software and program the module.

When you have to diagnose

 

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Category: Brakes, the bimmer pub

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