Have you ever noticed a yellow, triangle-shaped warning light with a circle around it on the dashboard of your BMW? It may appear sporadically or stay on permanently, and it could be accompanied by ABS and traction warning symbols. The yellow triangle warning light means there is a problem with the DSC system, which stands for dynamic stability control.
However, BMW DSC is a complex system whose operation relies on several sensors and devices. Tracking down the root of the problem is not always a straightforward job and can result in unnecessary repairs.
To help you narrow down the problem, we will take a look at what can cause BMW DSC failure and even give you tips on how to fix them.
Most Common Causes of BMW DSC Issues
1. Malfunctioning ABS Wheel Speed Sensor
BMW's DSC system determines vehicles' speed and movement using four sensors, one at each wheel. Because of their location inside the hub assembly, they are exposed to moisture and corrosion.
The same goes for the corresponding wiring and connectors, which may also get physically damaged. This can damage the sensor or cause poor connection that interrupts communication between the ABS module.
Additionally, the readings from the sensors may be incorrect, which confuses the DSC system and causes unusual behavior.
2. Corroded or Deformed Ring
Another common DSC system failure point is a metal band wrapped around the drive shaft called the reluctor ring.
It has a series of slots on its surface, which the speed sensor uses to determine how fast the wheel is spinning. With time, the ring may corrode and eventually bend out of shape.
Consequently, the deformed surface could start touching the speed sensor and damage it.
3. Faulty Steering Angle Sensor
Most modern BMW cars have a steering angle sensor that the DSC system uses to determine whether the vehicle is turning as the driver wants it.
The sensor itself rarely fails, although the wiring within the steering wheel column may break, causing DSC system failure. The clock spring behind the steering wheel is the usual weak point.
4. Accidental Disengagement
The driver, or one of the passengers, may unintentionally turn off the DSC system by accidentally pressing the button on the central console.
This would, however, only last until the car is turned off. The DSC system is designed to initiate itself upon every ignition. Still, the DTC button may be jammed or short-circuited, causing the DSC to turn off when the car is running.
DSC system relies on the ABS and its modules for a part of its function. If this component malfunctions, it may also cause DSC system failure or affect its operation. Still, these issues will usually trigger a range of brake-related warning lights.
6. Electrical problems
Like anything else electrical, a blown a fuse or poor battery connection can cause DSC failure. As with many other car problems, checking the fuses and battery connections is always a good starting point.
A weak battery no longer holding a charge can also disable the stability control system due to low voltage and, as a result, trigger the stability control light.
7. Insufficient grip
As obvious as it may sound, a lack of grip from the tires will cause the DSC light to flash as the system engages.
Although most drivers will notice if the tires on their car are bald and need replacement, there are several other possible issues. This includes worn shock absorbers and suspension misalignments, which can cause one of the wheels to lose contact with the surface beneath it.
Non-matching tire sizes can also be a reason why the stability control light comes on.
ABS related issues
ABS failures will also affect DSC operation, as these systems share several components. Things to look for include low brake fluid and failed ABS pump.
How to track down the issue
When the DSC light is on, the first step is determining what is causing the issue. This involves hooking up the car to a diagnostic device to see what is happening inside the DSC system. But to do so, you will probably need more than a simple scan tool, as most of them have no access to these modules.
Instead, you will probably need a BMW complete system scanner or an application like Carly. With access to all relevant control modules, you will be able to see if there are any stored error codes, which will help pinpoint the cause of the problem.
Even if there are no stored codes, you can observe if the readings from sensors make sense and match the actual conditions. For example, a speed sensor giving implausible read-outs will occasionally show that its wheel is spinning at different speeds from others.
Having determined the cause of the problem, you can now replace the faulty component. In most cases, this is an easy task to remove the old part and fitting the new one. There is, however, one thing to consider when dealing with faulty speed sensors, especially on the rear axle.
During replacement, you should check the condition of the reluctor ring. The easiest way of doing this is by inspecting the bottom side of the sensor for wear marks or scratches. If there are any, the reluctor ring is either bent out of shape or corroded. You should first take care of that, as otherwise, the new sensor will become damaged again.
Once the component causing the DSC failure has been replaced, the system will, in most cases, resume its function. The only exception is the steering angle sensor, which needs to be recalibrated after replacement. This is following a specific calibration procedure and with the help of the diagnostic device.
Frequently Asked Questions
Can I drive when the DSC light is on?
- DSC system is an important safety feature that significantly improves vehicles' stability in slippery road conditions. It prevents wheels from spinning during accelerations and stops the back end from skidding when going through bends. Because of that, driving a vehicle when the DSC light is on is not recommended, as it can lead to an accident.
- Still, if you need to use your BMW with a failing DSC system, drive moderately end with extra caution. But for your own safety, have the problem fixed as soon as possible to avoid any potential accidents.
What to do when the DSC system failure causes a power loss?
- A DSC failure can cause the traction control to kick in a while driving, although there is no apparent reason for it to do so. This usually happens if your BMW interprets faulty speed sensors readings as a wheel spin. As a result, the DSC system will cut the engine power, reducing vehicles' overall performance. The easiest way of temporarily getting around this problem is by shutting down the system. This can be done either through the iDrive or by pressing the DSC button for several seconds.
As we explained, a DSC light is a triangle-shaped warning light with a circle around it symbolizes issues with BMW's DSC system. This light will illuminate the dashboard when it intervenes to stabilize the car while driving or when there is a DSC system failure. The most common failure points are ABS speed sensors and reluctor rings. Other likely possibilities range from malfunctioning steering angle sensors to poor battery connection or even low brake fluid.