If you have been a BMW owner for quite some time, you have probably experienced the DSC light before.
The DSC system is a really great function to have on your car in regards to safety.
Unfortunately, the DSC system contains a lot of sensitive sensors and electronics, 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 to maneuver the car when oversteering or understeering. DSC analyses the speed of individual vehicle wheels and whenever it senses that the driver is losing control of the car, it activates ABS for that wheel and even shuts off engine power.
All this is done via sensors attached to the wheels. The information from the sensors, together with the information from many other sensors, is sent to the DSC control unit for processing and calculation.
DSC Light Causes
If the DSC is activated the moment you start driving, it could be a symptom of one of the wheel sensors. Other causes are the wiring of the sensors to the DSC console or the ABS. When driving, DSC is activated and this is the default position. It works in conjunction with the automatic transmission, the ABS wheel sensor, and the brake pedal. Each time DSC detects that one of the wheels loses traction, DSC activates all the above functions.
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 this time.
How to fix it
There are many reasons why the DSC light could be on. Here are a few tips that you should do/check when the DSC light on your dashboard comes on.
Check whether DSC is on
The first thing to do when your DSC is off is to check that the DSC is active. If it was pressed by mistake, you can restore the DSC by simply pressing the DTC.
The easiest and cheapest way to solve a lit up DSC Light is to use an OBD2 scanner to read the fault codes. The cause of the problems varies and you may need to see a certified mechanic to properly diagnose the problem.
There are cheap scanners that you can buy, or you may have to take the car to a mechanic to read the fault code memory. If you are interested in getting one for yourself, you will find some good ones here: Best OBD2 Scanners. Just remember that older BMWs do not use the regular 16-pin OBD plug.
An error code can often help you solve the problem and give you hints on where to start looking for the problem. In BMW vehicles, the OBD2 plug is usually located under the steering wheel. On some older BMWs, the diagnostic port is located under the bonnet. You can do an online search of the fault 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 over- and understeering. When the brake fluid runs out, the ABS and DSC lights come on. In some cases, you may have old brake fluid that becomes acidic. If the brake fluid is low, top it up with a recommended brand.
Defective wheel sensors
Each wheel has sensors that collect important information about the car’s wheel speed and transmit it to the DSC. Over time, the sensors become clogged with dirt and other deposits. You can clean the sensors with special wheel cleaning solutions. If the sensors are completely ruined, replace them with new ones. Also, check the cables connected to the sensors. These could be missing or broken.
A sure-fire way to determine if the problem is with the sensor and not the wiring is to swap the right sensor with the left one. 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 if you still have a wheel sensor error code, you know that the problem is with the sensors.
Faulty ABS pump
The DSC works with ABS to bring a car under control during skidding. If the ABS fails, the DSC gives you an error code. To rectify this, remove the key from the ignition, unplug the ABS connector and reconnect it. As soon as you start the car again, you should notice that the DSC light has gone out.
The other problem that keeps your lights on is a faulty ABS pre-charge pump. This will be the case if you have an old BMW. Initially, the lights will come on at high speeds, but over time they will stay on constantly. If you use a scanner, you will notice that the error codes refer to the pre-charge pump.
The reason for this is worn 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.
Malfunctioning ABS Control Unit Module
A defective ABS control module is fortunately unusual in BMW vehicles. If you scan your error codes and their instances, you will find an internal failure of the control unit. This can start as an occasional flashing yellow light before it becomes permanent. In most cases, the ABS pump will begin to fail, affecting the brake lights, DSC, and ABS.
The ABS control unit has solder joints that break over time. By unplugging and replugging the module, you can check if it is the ABS control unit that is malfunctioning. If you still receive a communication error, then you know that your ABS module may be defective.
Replacement is possible. You can purchase the BMW ABS Rebuilt Service with the ABS module. These are often found in many car workshops and will set you back around $200. Repairing the ABS pump will cost you around $600 to $800.
The ABS repair service does not require any additional coding, but you must bring the vehicle’s VIN for the ABS pump. You can delete the codes in the system using a scanner, and the unit will continue to work properly. Please note that on older BMW models, the odometer and speedometer will not work if the ABS module is deactivated.
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 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 on. Finally, the steering angle sensor must also be checked, as the DSC light will also come on if this malfunctions.
The BMW DSC is an indispensable system when it comes to correcting oversteer or understeer. It uses a series of sensors on each individual wheel to monitor speed. The moment it detects that the driver is losing control, it activates ABS and also reduces engine speed. As a result, the driver has better control of the vehicle and can avoid skidding.