When BMW Anti-lock Braking System (ABS) module or pump fail, you will notice at least one of the following symptoms:
- ABS light stays on
- DSC warning light
- The speedometer may stop working as well.
- An orange or red BRAKE warning light may come on at the same.
- ABS pump constantly running
- Battery draining when a vehicle parked
- Braking and dynamic response system malfunction. Drive moderately. Avoid hard braking Message on iDrive
Reading the codes will help you pinpoint why your BMW DSC and ABS are staying on.
If the DSC light comes on as soon as you start to drive, this typically indicates a problem with wheel speed sensors. But it can also be an issue with the wheel speed sensor wire or the ABS module.
Can I drive if the ABS/DSC light is on?
Depending on the problem, it may be possible to continue driving with caution. While you can still drive your BMW even if the DSC light is on, you may be more likely to get into an accident under extreme maneuvers or inclement weather conditions.
Do not drive if the BRAKE light stays on.
Diagnose your BMW as soon as possible. A problem with the brake system could result in a fatal accident.
What is BMW DSC?
DSC stands for Dynamic Stability Control. Its main purpose is to monitor the vehicle and help keep it stable and driving in the intended path. The DSC system is always enabled by default. Under normal operation, the light DSC light on the instrument cluster should be off.
DSC system monitors your BMW input from several sensors to determine if the vehicle is driving in the intended path.
For example, the DSC analyzes data from the steering angle sensor, yaw rate sensor, ABS wheel speed sensor, automatic transmission, brake pedal, etc. If it detects that the vehicle is losing traction or wheels are spinning, it will apply brake pressure to keep the BMW on the right path.
How to Diagnose BMW DSC codes
To diagnose BMW ABS problems, you will need a BMW Scanner to read fault codes from the DSC and ABS module such as Foxwell for the BMW OBD-II scanner.
Locate the OBD2 port on your BMW. It is under the dashboard next to the hood release. Plug your BMW scan tool.
Turn on the ignition but do not start the car. The key should be in position II. All dash lights will turn on when the key is in position II.
Read codes from the DSC module. Research the error code online. Consult an independent BMW shop or the BMW dealer if necessary to better understand the problem, causes, and possible solutions.
Address the problem. Once you fix the problems, reconnect the BMW scanner and clear the fault codes.
Drive your BMW even if it is for a few minutes to see if the DSC light will come back on. DSC light is generally triggered as soon as you start to drive especially if there is a problem with the ABS pump or the wheel speed sensors. That's why you should always drive your BMW and verify the DSC light doesn't come back on. Once you perform a test drive, rescan for codes to be sure.
You won't be able to clear the fault codes until you fix the issue that triggered the code in the first place. Codes triggered in the past but currently are not an issue or action will be saved as shadows or stored codes. Those can be erased.
If the module doesn't respond, it is possible that the ABS module is faulty, or you have a generic scanner that can not read ABS codes. Try unplugging the wire harness from the ABS module and reconnecting it.
Here is a list of typical BMW problems that can trigger the DSC / ABS/ Brake lights. We strongly recommend that you read the fault codes before you replace any parts.
Always read the codes and consult an auto mechanic specializing in BMWs or the dealer for more help.
ABS Wheel Speed Sensor
The wheel speed sensor (or ABS wheel sensor) is one of the most common problems causing the DSC light to come on. These sensors fail due to water damage, dirt, or metallic particles collected on the sensor's magnetic part.
It would be best to replace the wheel speed sensor without first confirming it is the culprit. Replacing a wheel speed sensor is easy on a BMW, but don't throw parts at your beemer if it doesn't need it. Read the codes before you replace the wheel speed sensor.
If you replaced the wheel speed sensor and are still getting the same error related to wheel speed sensor failure, the wires to the sensor may be damaged, or the ABS Control unit is the problem.
One way to confirm that the sensor itself is the problem and not the wires or the ABS module is to read the codes. Let's say it points to a bad right rear wheel speed sensor. Swap the two rear sensors and drive the car.
Did the error move to the other wheel? If it did, you know the wheel speed sensor's problem because the error moved with the sensor. If the error is still pointing to the right rear wheel, you may have a cut wire or a bad ABS module.
When replacing BMW wheel speed sensors, it is strongly recommended to stay with the OE BMW wheel speed sensor. Aftermarket BMW wheel speed sensors tend not to last as long and, in some cases, don't work properly.
ABS Control Unit Module Malfunction
The ABS pump may fail and trigger the DTC / ABS / Brake lights. In most cases, if you scan your BMW, you will get code descriptions such as "control unit internal failure." At first, you may notice these lights intermittently, but eventually, they will come on and stay on consistently.
In some cases, the yellow warning lights come when the car warms up and may go away when the car cools down. Broken solder joints often cause these symptoms in the ABS module circuit.
You can try unplugging it and reconnecting to see if that fixes your DSC problem. Suppose you are getting a "Communication Error" when you try to scan the ABS module, signifying that the module may be defective.
If your ABS module fails, one of the cheapest ways to fix it is to use a BMW ABS rebuilt service. These are shops that specialize in fixing these common problems on BMW ABS modules. A BMW ABS rebuilt service can cost under $200 and doesn't require any coding.
A new ABS pump costs over $600-$850. On newer BMWs installing a new ABS pump will require coding to your VIN. If you take your car to any BMW dealer, this repair cost is $1000-$1500. When you rebuild your existing ABS pump, there is no need to pay money for coding. You may need to clear stored codes, though.
You can do that yourself using a scan tool that can read and clear BMW fault codes.
There are third-party companies that provide BMW ABS Module rebuild which you can order on eBay. Within six to ten days, you will typically get back your repaired ABS unit. Install it back on your BMW. Clear the stored fault codes, and you are ready to go.
Cars back in the 1990s didn't have ABS, and your BMW will be in the same situation. The speedometer and odometer will also not work with the ABS module removed.
Neither will your instrument cluster record any added miles. You will also trigger additional fault codes that will require a BMW specific OBD2 scanner to be erased.
If you remove the ABS module, it is recommended to cover the ABS block to avoid the environment to cause any damage or corrosion.
If you have an older BMW, you may be able to get away with installing a used ABS hydraulic unit without coding. Newer models need coding unless it is the original unit, or you will get errors such as PT-CAN chassis number wrong or ECU not initialized.
ABS Pre-charge Pump Motor Failure
The pre-charge ABS pump may fail. This is common if your BMW has high miles, and you notice the lights at high speed, such as over thirty mph, or when you drive your car as if you stole it.
Eventually, the lights will come on and say on all the time. When you scan your BMW, you will get error codes related to the pre-charging pump.
The reason why this happened is often the worn brushes inside the ABS pump. The more miles on the BMW, the more likely it is for these brushes to wear out.
To check if this is your problem, try accelerating very slowly. If the lights don't come on, this may indicate that the precharge pump is the problem. Always read the fault codes to verify that the pre-charge pump is the culprit before you replace it.
To replace the pump, you will need to bleed the brake system. Remove the pump and install the new one.
Since the pump is simply an electrical motor, installing a used pump would be fine as long as it is the same part number. Another alternative would be to open up the motor and replace the brushes yourself.
ABS Pressure Sensor
If your BMW has the DSC and the brake light on, the problem may likely be the pressure sensor mounted in the brake cylinder. In most cases, the ABS light does not turn on, only the DSC and brake light. Codes that may present when you scan the DSC module include:
- 5E24, 5E20 - Pressure Sensor 1 Faulty
- 5E21 - Pressure Sensor 2 Faulty
To verify the sensor is the culprit, you can swap the two sensors. Let say the error code pointed to Sensor 1, but after the swap, it now moved to Sensor 2 location. You know that the problem is the sensor. If you are still getting the error code pointing to sensor 1, the problem is likely the ABS unit and not the sensor.
Low Brake Fluid Level
Low fluid levels can trigger the brake light and, in some cases, the DSC warning light as well. Open the hood of your BMW and locate the brake fluid reservoir.
Look at the translucent reservoir and identify the Max and Min marks. If the level is below the LOW mark, you need to add brake fluid. Always use the recommended BMW brake fluid.
If you are getting an error message Brake Fluid Level Low, the brake fluid level sensor may be defective or disconnected.
Steering Angle Sensor
The steering angle sensor located in the steering column under the steering wheel can also cause the DSC light on.
This is a less common problem but worth checking. To check the power steering angle sensor, you will need a scanner such as Foxwell NT510 for BMW
to display live data from the steering angle sensor.
Brake Light Switch
The brake light switch may also fail and triggered the DSC light on. The brake light switch is mounted above the brake pedal and removed in less than fifteen minutes.
High voltage or low battery voltage may trigger the DSC light and other lights on BMW.
This can be caused by a faulty alternator, a bad voltage regulator, or a defective BMW battery. BMW cars are susceptible to low voltage.
If that is the problem, you may notice other problems such as BMW going into limp mode.
- Pressure Sensor Not Plausible
- Wheel Speed Sensor Front Right Start Recognition
- Error Number such as 17FE
- Control Unit Internal Failure
DSC Turned Off
The first thing you should try is to press and hold the DSC button on your dashboard. The button may have been pressed accidentally and disabled the DSC.