If you have owned a BMW for some time, you have probably already experienced the DSC light.
The DSC system is a very good feature to have on your car when it comes to safety.
Unfortunately, the DSC system contains many sensors and sensitive electronic components, and these components are all known to fail after a few years.
What Does the DSC Light Mean?
DSC stands for Dynamic Stability Control and is a system that helps the driver maneuver the car during oversteer or understeer. The DSC analyzes the speed of the vehicle’s individual wheels, and whenever it detects that the driver is losing control of the car, it activates the ABS for that wheel and even cuts engine power.
DSC Light
All of this is done via sensors attached to the wheels. The information from the sensors, along with data from many other sensors, is sent to the DSC control unit for processing and calculation.
Causes of the DSC Light
If the DSC is activated at the moment you start driving, it could be a symptom of one of the wheel sensors. Other causes are the wiring from the sensors to the DSC console or to the ABS. While driving, the ASN is activated and that is the default position. It works in conjunction with the automatic transmission, the ABS wheel sensor, and the brake pedal. Whenever DSC detects that one of the wheels is losing traction, DSC activates all the functions mentioned above.
In BMWs, it is possible to deactivate the DSC. This is done by pressing the DTC for three seconds. Please note that the DSC will have no control over your vehicle at that time.
How to Fix It
There are many reasons why the DSC light might be on. Here are some tips on what you should do/check when the DSC light on your dashboard comes on.
Check if DSC is Activated
The first thing to do when your DSC is off is to check that the DSC is active. If it was accidentally pressed, you can restore the DSC by simply pressing the DTC.
OBD2 Scanner Tool
The easiest and cheapest way to resolve an illuminated DSC Light is to use an OBD2 scanner to read the error codes. The cause of the problems varies, and you may need to consult a certified mechanic to properly diagnose the issue.
There are inexpensive scanners you can buy, or you may need to take the car to a mechanic to read the error code memory. If you want to get one for yourself, you can find good ones here: Best OBD2 Scanners. Just remember that older BMWs do not use the standard 16-pin OBD port.
An error code can often help you solve the problem and tell you where to start looking for the issue. In BMW vehicles, the OBD2 port is usually located under the steering wheel. On some older BMWs, the diagnostic port is located under the hood. You can search online for the error codes to find out exactly what the problem is.
Brake Fluid Levels
The DSC works in conjunction with the ABS to bring the car under control during oversteer and understeer. When the brake fluid is low, the ABS and DSC lights come on. In some cases, you may have old brake fluid that has become acidic. If the brake fluid level is low, top it up with a recommended brand.
Faulty Wheel Sensors
Each wheel is equipped with sensors that collect important information about the car’s wheel speed and transmit it to the DSC. Over time, the sensors get clogged with dirt and other deposits. You can clean the sensors with special wheel cleaning solutions. If the sensors are completely damaged, replace them with new ones. Also check the cables connected to the sensors. These could be missing or broken.
A foolproof way to determine if the problem is with the sensor and not the wiring is to swap the right sensor with the left sensor. This is not possible on some models because the sensors on both sides are different. It can also be very difficult to remove the sensor without destroying it. However, if you successfully remove both sensors and you still have a wheel sensor error code, you know the problem lies with the sensors.
ABS Control Module
The DSC works with the ABS to bring a car under control during skidding. If the ABS fails, the DSC gives you an error code. To fix this, remove the key from the ignition, disconnect the ABS connector, and reconnect it. As soon as you restart the car, you should notice that the DSC light has turned off.
The other issue that keeps your lights on is a faulty ABS precharge pump. This will be the case if you have an old BMW. Initially, the lights will come on at high speed, but over time, they will stay constantly on. If you use a scanner, you will notice that the error codes refer to the precharge pump.
The reason is the wear of the ABS pump brushes. Before installing a new ABS pump, the brake system must be bled. The ABS pump is an electric motor, and you can replace your old pump with another set as long as it has the same part number.
It is difficult to find ABS pumps for certain BMW models.
Faulty ABS Control Unit Module
A faulty ABS control module is fortunately uncommon in BMW vehicles. If you scan your error codes and their instances, you will find an internal failure of the control unit. This may start with an occasional flashing yellow light before it becomes permanent. In most cases, the ABS pump will start to fail, affecting the brake lights, DSC, and ABS.
The ABS control unit has solder joints that break over time. By disconnecting and reconnecting the module, you can check if it is the ABS control unit that is malfunctioning. If you still get a communication error, you know that your ABS module may be faulty.
Replacement is possible. You can purchase the BMW ABS Rebuilt service with the ABS module. These are often found in many auto repair shops and will cost you around $200. Repairing the ABS pump will cost you about $600 to $800.
The ABS repair service does not require any additional coding, but you must provide the vehicle’s VIN for the ABS pump. You can clear the system codes using a scanner, and the unit will continue to function properly. Please note that on older BMW models, the odometer and speedometer will not work if the ABS module is disabled.
Faulty Pressure Sensor
If you notice that your BMW brake lights and DSC are always on, the problem could be with the brake cylinder pressure sensor. If you perform a scan, you will receive codes 5E21, 5E24, or 5E20. This will reveal a faulty pressure sensor, either 1 or 2. To clearly see that these sensors are the culprits, you need to swap the two sensors and check that the error code is still active. Finally, the steering angle sensor should also be checked, as the DSC light will also come on if it malfunctions.
Conclusion
The BMW DSC is an essential system for correcting oversteer or understeer. It uses a series of sensors on each individual wheel to monitor speed. As soon as it detects that the driver is losing control, it activates the ABS and also reduces engine RPM. As a result, the driver has better control of the vehicle and can avoid skidding.