The Dynamic Stability Control (DSC) system is one of the most reliable systems in BMW. When compared to other in-car systems, the DSC will usually operate trouble-free for decades. However, DSC faults do happen.
The most common DSC faults are related to faulty wheel speed sensors, chaffed/corroded wiring, power supply, and corroded hydro block valves and pumps. On older E Series models the corroded driveshaft CV joints can distort sensor reluctor rings causing erratic sensor readings.
What is DSC?
Dynamic Stability Control is an advanced BMW version of the Electronic Stability Control (ESC) system. In BMW it is part of complex Driving Stability Control which includes, depending on a model series and equipment, many other control modules like ACSM (Air Bag), EPS (Electrical Power Steering), HSR (Rear Axle Slip Angle Control), VDP (Vertical Dynamics Platform), VTG (Transfer Case), and so on…
Dynamic Stability Control (DSC) is the primary component of the driving dynamics control systems used to promote active safety, along with the Vertical Dynamics Platform (VDP). It improves traction when accelerating and taking off as well as driving stability under all conditions.
Additionally, it assists in keeping the car stable and recognizes risky driving conditions including under or oversteering.
The Evolution of Dynamic Stability Control
Beginning with the 1986 model year, every BMW sold in the United States came equipped with ABS brakes as standard equipment, making it one of the first manufacturers to adopt anti-lock braking systems to cars. In the late 1980s, BMW released Automatic Stability Control (ASC), the company’s first traction control system. The technology was improved throughout the 1990s to offer even more stability control capability.
This improved system, known as All Season Traction, became a requirement on every BMW sold in the United States in 1996. Many new features, including Cornering Brake Control, were added to All Season Traction as it continued to develop.
Dynamic Stability Control (DSC), BMW’s most sophisticated Electronic Stability Control system, was first introduced in the 1990s and became a standard feature on all BMW passenger cars and light trucks sold in the United States starting with the 2000 model year.
Most Common DSC Problems
Besides a few software-related issues solved with the next release, the most common DSC problems are related to failed wheel speed sensors, wiring issues, power supply, and the module itself.
Wheel Speed Sensors
Wheel speed sensors on modern BMWs are as reliable as it gets and they fail very rarely because of design or manufacturing defects. However, they are often damaged during the repair work as sometimes they can be very hard to remove. This problem mostly affects older BMWs with iron wheel hub carriers.
When the tortured sensor is installed back problems will usually arise down the road, often after a few years. The sensor housing plastic usually cracks and the sensor internals slowly corrode.
Beware that in the early E Series, the sensor faults are often related to driveshaft reluctor ring corrosion. Basically, the CV joint corrodes and distorts the reluctor ring and wheel speed sensor clearance.
Chaffed Wiring And Poor Contacts
This is a known problem from E70 X5 where the wiring harness to the DSC acceleration sensor is tensioned too tightly, causing either a cut wire on sharp body edges or a poor connector contact at the sensor.
In addition to design-related issues, accidents or repair work often result in wiring damage. The taste of german wires is also a favorite among rodents, depending on where you reside.
Troubleshooting the issue could take you hours, just like with any electrical issues. In such circumstances, ISTA test plans and wiring diagrams are invaluable.
The fix for the cable break repair the damaged wire and shield the wiring section from edges that could cut it. Always make sure that the cable is not too tight as this could cause poor connector contact.
Brake Binding Due to Corroded DSC Valves
Mechanical issues with the DSC modulator or hydraulic block are extremely rare. However, they do happen with poorly maintained BMWs. Besides affecting the most important system in your car, mechanical faults in the DSC unit will not trigger any warning light or check control message. So, besides losing the brakes this is the most dangerous DSC fault.
The symptoms are similar to problems with brake calipers. Common complaints often include pulling to one side while braking or sticking brakes even after releasing the brake pedal. This fault is a reason most BMW owners learn about DSC’s water-cleaning function when raining.
Based on the speed of the windscreen wipers, the DSC adjusts lower brake pressures via periodic, cyclical regulation. The brake pads are applied repeatedly. During the process, the brake discs are routinely cleaned. No quantifiable vehicle slowing results from this. The frequency and duration of brake pad application depend on:
- The intensity of rain, based on the windscreen wiper speed
- Driving speed greater than 45 mph
When the windscreen wipers are active the brakes are automatically applied to remove the water film from the brake discs. When the system functions as it should, you can’t notice it. But when the DSC hydraulic valves malfunction, the vehicle can slow down drastically without depressing the brake pedal.
A customer recently complained that F30 3 Series slowed down from 100 mph to under 60 mph in spite of the gas pedal being depressed to the floor.
The systems most sensitive to “no maintenance” are those installed in E Series M5/M6, 1/2 Series F2x, and 3/4 Series F3x. In fact, if you don’t change brake fluid for 10 years, you can count on it.
The solution to the problem is replacing or rebuilding DSC hydraulic unit. To prevent this problem from ever happening, just follow the usual maintenance schedule and change the brake fluid every two years by using only quality fluids. Since they are cheap and you’ll only need a quart, treat your BMW with a genuine BMW part.
Failed DSC Pump Motor
This is the common failure with 2004 – 2012 1, 3, Z4, and M5/6 E Series. When the pump motor fails, you’ll get a standard DSC malfunction warning and brake light. Fault memory readout will reveal these codes:
5DF0 Hydraulic unit: pump motor 5DF1 Hydraulic unit: pump motor connector fault
These errors usually appear sporadically at the beginning, but over time they become permanent. The problem is either worn electric motor carbon brushes or water ingress into the pump’s electrical motor which inevitably leads to corrosion and total failure.
The solution is to replace the DSC module or repair the electric motor.
Since cars are typically old when this defect occurs, the cost of a new DSC unit frequently exceeds the value of the vehicle. Fortunately, there are many companies today that specialize in rebuilding DSC units, as well as DIY repair kits.
Be aware that you will need to encode the module and reset the steering angle sensor if you choose to replace the DSC with either a new or used unit.
Also, after replacing the hydraulic unit you’ll need to properly bleed the brake system which requires performing a brake bleeding service function with ISTA or another capable scanner.
DSC Voltage Supply
Just like any control module, the DSC requires a stable power supply. A lot of power supply. The most common voltage supply issues are related to a weak battery or poor B+ terminal contacts.
As soon as you push the start button to start the engine, the DSC module will quickly run the system check. If the battery is weak or the voltage supply is low at this point the system “Driving Stabilization” warning message will pop up in your instrument cluster and iDrive display.
If the battery is weak, the voltage will drop below a safe threshold (<9V) during engine start and if the alternator can not lift the voltage fast enough, the DSC system check will fail.
These are the most common fault codes in case of low voltage supply:
5DF8 DSC: Undervoltage 5DF4 DSC: Battery voltage too low, open circuit
To troubleshoot the voltage supply problem you’ll need the specific wiring diagram for your BMW. Let’s have a look at the 2007 BMW E90 330i.
As you can see in this diagram, all the power supply to the DSC module comes from Junction Box (A4010) located in the passenger footwell behind the glove box. In this case, we can follow the B+ positive battery cable from the battery in the trunk up to the fuse box (Junction Box) and compare the voltage on fuses F35, F65, and F20 with the battery voltage.
Unless modified by a recall campaign, for most E90s the power supply of the junction box itself is the weakest point.
If the voltage correspondence to those of the battery, we can move on to the DSC module connector and check the voltage supply at pins 32, 1, and 17 between the grounds at pins 16 and 47. If the voltage supply and grounds are good, the problem is in the DSC module.
Steering Angle Sensor Fault
Steering angle faults will trigger DSC faults as this is one of the most important data DSC needs to operate. Although not often, steering angle sensors do fail, no matter the model series. The fault memory readout will reveal a steering angle sensor fault.
When the steering angle sensor fails, you’ll need to replace the coil spring or the complete steering cluster unit (SZL). After the replacement of the coil spring, you’ll need to calibrate the steering angle. If you are replacing the SZL module, you’ll need to encode it before the steering angle sensor adjustment.
However, steering angle faults can sometimes become complicated.
Recently I was chasing a bunch of DSC-related faults in the 2018 F80 M3. The car had an accident and was brought in to solve a series of other faults. The DSC faults were all related to the DCS interface and missing signals from both the DSC, SZL, and ICM. Although the steering angle sensor calibration went successfully, the DSC malfunction light would light up as soon as you start driving.
Further research revealed the steering rack was replaced after the accident but was installed incorrectly. That is, when the mechanic installed a new steering rack it was not positioned at the mark (middle). So you could steer slightly more to the left than to the right. Or vice versa, I don’t remember exactly.
After installing the steering rack the right way all faults were gone.
Even slightly incorrect wheel alignment causes exactly the same faults as the incorrectly installed steering rack.
A system that is completely functional can nonetheless experience a DSC fault. For instance, when the rear axle is raised when towing (the trailer weight is not balanced), when the wheels are spinning on a vehicle hoist, or when the brake roller test is being performed. The DSC module detects implausible wheel speeds and switches off stability control completely.
The fault codes are stored on safety grounds, so they cannot be erased until the ignition is cycled off and on and the car is driven again.
The DSC system is just another reminder that BMW is the industry leader in active safety technology. The technology has proven to be reliable over time, but as the car gets older, faults are bound to become more frequent. Sometimes, troubleshooting complex, advanced systems can be a genuine pain.
Working on such systems calls for a skilled expert, expertise, specialized equipment, and most importantly, high-caliber workmanship.
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