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 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 a driver maneuver the car during over/understeering. The DSC analysis the speed of individual car wheels and whenever it senses that the driver is losing control of the car, it will activate ABS for that wheel and even cut engine power.
All this is done through sensors attached to the wheels. Information from the sensors is passed on to the DSC control unit, together with information from a lot of other sensors for processing and calculating.
DSC Light Causes
If the DSC is activated the moment you start driving, it could be a symptom with one of the wheel sensors. Other causes will be the wiring from the sensors to the DSC console or the ABS. When driving the DSC is activated and this is the default position. It works in conjunction with the automatic transmission, ABS wheel sensor, and brake pedal. Anytime the DSC detects that any of the wheels are losing traction then the DSC will activate all the above.
In BMW’s it is possible to disable the DSC. This is done by pressing the DTC for three seconds. Note that the DSC will not be control of your car at this time.
How to fix it
There are a lot of causes of why the DSC light might be on. Here are a few tips that you should do/check when the DSC light lightens up on your cluster.
Check whether DSC is on
The first thing to do when your DSC is off is to check whether the DTC is active. If it was pressed accidentally you can restore the DSC by simply pressing the DTC.
The easiest and cheapest way to solve a lighten up DSC Light is to use an OBD II scanner to read the error codes. The cause of the problems vary and you may need to see a certified mechanic to properly diagnose the problem.
There are cheaper scanners that you can purchase, or you have to take the car to a mechanic to read the trouble code memory. If you are interested in getting one yourself, you can find some good here: Best OBD2 Scanners. Just remember that older BMW’s do not use the regular 16 pins OBD connector.
However, a trouble code can often help you solve the problem and give you guidance of where to start looking for the problem. On BMW Cars the OBD II port is usually located underneath the steering wheel. Some older BMW’s uses a diagnostic port under the hood. You can perform online research on the error codes to find out exactly what they are about.
Brake fluid levels
The DSC works with the ABS to bring the car in control during over/understeering. When the brake fluid is low you will have the ABS and DSC light coming on. In some instances, you could have old brake fluid that causes it to become acidic. If the brake fluid is low top it with a recommended brand.
Defective wheel sensors
Each wheel has sensors that collect and pass vital information about the car’s wheel speed to the DSC. The sensors with time become clogged by dirt and other debris. You can clean the sensors with special wheel cleaning solutions. If the sensors are completely spoilt, then you will need to replace them with new ones. Also, check the wires connecting to the sensors. This could be lost or broken.
One sure way to know whether 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 are different on both sides. 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 an error code of the wheel sensors then know that the problem is with the sensors.
Faulty ABS pump
The DSC works with the ABS to bring a car into control during skidding. When the ABS malfunctions then you are going to have an error code with the DSC. To solve this, remove the key from the ignition and unplug the ABS then connect it again. Once you restart the car you should notice that the DSC light has gone off.
The other issue that will keep your lights on will relate to a faulty pre-charge ABS pump. This will be the case if you have an old BMW. At first, the lights will come on when you are doing high speeds than with time it will constantly be on. Using a scanner you will realize that the error codes relate to the pre-charging pump.
The reason for this is worn out ABS pump brushes. Before installing a new ABS pump, bleed the braking system. The ABS pump is an electrical motor and you can replace your old one with a different set as long as it is of the same part number. It is hard finding ABS pumps for particular BMW models.
Malfunctioning ABS Control Unit Module
A faulty ABS control module is unfortunately uncommon on BMW cars. When you scan your error codes their instances you will notice the control unit internal failure. This may begin as occasional flashing yellow lights before they proceed to a permanent basis. Most of the time the ABS pump starts malfunctioning it will affect the brake lights, DSC, and ABS.
The ABS control unit has solder joints that break with time. You can confirm that it is them that have a problem by disconnecting the module and plugging it back in. If you still get a communication error then know that your ABS module may be defective.
Replacement is possible. With the ABS module, you can purchase the BMW ABS rebuilt service. These are often found in many auto repair shops and will set you back to around $200. Fixing the ABS pump will cost you around $600 to $800.
The ABS rebuilt service does not require any additional coding but you will be required to come with the car’s VIN for the ABS pump. You can clear the codes in the system through a scanner and the device will continue working fine. Note that in 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 light and DSC are always on them the problem could be the brake cylinder pressure sensor. When you perform a scan you will get 5E21, 5E24, or 5E20. This will reveal faulty pressure sensor 1 or 2. To clearly identify that these sensors are the culprits then you need to swap the two sensors and check whether the error code is still on. Lastly, also check the steering angle sensor, this if malfunctioning will turn on the DSC light.
The BMW DSC is an essential system when it comes to correcting over/understeering. It uses a set of sensors on each individual wheel to check for speed. The moment it detects that the driver is losing control, it will set the ABS in motion and also lower engine speed. This leads to the driver having better control of the vehicle and avoiding skidding.