BMW Steering Switch Unit (also referred to as SZL, center steering column switch, and switch unit in the steering column) is mounted on the BMW steering column where various switches, including a wiper, turn signal, cruise control mounted.
The steering angle sensor is integrated into the SZL unit. SZL and steering angle sensors can fail on any BMW, causing any switches to stop working or trigger various warning lights.
When the steering angle sensor fails, it triggers warning lights; most often, the DSC lights can come on randomly or as you start to drive.
When the SZL module or steering angle sensor fails, the car will drive fine, but you may not have traction control, stability control enabled, or functioning switches.
This problem has affected many BMW models, including 1, 3, 5, 7, X1, X3, X5, etc.
What is the BMW SZL module?
The SZL module is mounted behind the steering wheel.
SZL (steering switch unit) module is not the same as the steering angle sensor. The steering angle sensor is integrated into the SZL, but SZL has other functions and purposes than the steering angle sensor.
BMW SZL module is often confused with the steering wheel button switch module, which is behind the airbag (in the steering wheel) and controls the steering wheel buttons. The SZL module is below the steering wheel and contains a telescoping wheel switch, a heated steering switch, a wiper switch, a turn signal, and a clock spring.
How do you know if it is a bad steering angle sensor or SZL
A failed steering angle sensor fails frequently and triggers warning messages plus Brake, DSC, and ABS lights.
If the DSC malfunction or any instrument cluster warning lights related to ABS or traction control come on randomly when you start to drive or take turns, the most likely cause is a dirty steering angle sensor.
If any of the switches mounted on the SZL module, including turn signals, wipers, or cruise control, don't work, the problem could be the SZL module and not the steering angle sensor or clock spring.
Replacing the SZL module can be very expensive, ranging from $800 to $1500. The great news is that there may be a possible inexpensive fix for this problem.
You can even perform yourself. If you have been quoted hundreds of dollars for SZL replacement because ABS, DSC, traction control lights are on due to a failed steering angle sensor, you should first try cleaning the steering angle sensor as instructed below.
Cleaning the steering angle sensor is easy and, in most cases, fixes problems related to warning lights on the dash.
Note that BMW dealerships will not clean the steering angle sensor. BMW dealers will only replace the SZL unit or repair it if BMW issues a Technical Service Bulletin. If you have determined that the steering angle sensor is the culprit, we will show you how to remove the SZL, open up the steering angle sensor, and clean it.
If cleaning the steering angle sensor fails, you can still save money by replacing the SZL unit yourself.
The good news is that you can easily replace the SZL module and let the BMW dealer or Bimmer auto repair shop code it for you for around $80-$120.
Replacing the SZL yourself is a lot cheaper than having an auto repair shop or dealer replace it. Replacing the SZL module is so easy you can change it on your driveway.
Just don't forget to code the SZL module to match the steering wheel features of your BMW.
New BMWs require that you also write the VIN into the SZL to match that of your BMW. Instructions on how to change the BMW SZL module are provided below.
The optical sensor or potentiometer in the steering angle sensor (which is mounted on the SZL) can cause the failure of Active Steering, DSC (Dynamic Stability Control), ARS (Active Roll Stabilization), AHL (Adaptive Headlights), ACC (Active Cruise Control) and the automatic turn signal resetHeadlights), ACC (Active Cruise Control) and the automatic turn signal reset function.
The symptoms caused by a defective SZL are different than a faulty steering angle sensor. A steering angle sensor optical sensor in the SZL can fail and trigger various warning lights. If the SZL unit is defective, any of the steering column switches may stop working. Knowing which component is defective is important.
The following symptoms are only a guideline. You must read fault codes to properly diagnose a BMW.
Symptoms of a faulty steering angle sensor
If the SZL module fails on your BMW, you may experience any of the following problems. Typically the problem starts with a random warning message on the instrument cluster, which may go away and come back again randomly.
Warning messages as soon as you drive or turn the steering wheel
DSC Malfunction Drive Carefully
Reduced vehicle stability under acceleration and in curves. Drive at moderate speed.
Ensure that if you are purchasing a used SZL, you get one with the same part number. Different revisions may be available for the same chassis. Your SZL may need to be coded to your vehicle to match your car options such as Paddle Shifter, Multi-Function Steering Wheel button, heated steering wheel, etc.
Once the SZL module or steering angle sensor is removed, it needs to be coded, and the steering angle sensor needs to be calibrated. This requires that you have an advanced BMW scan tool. Such tools can be expensive. An alternative is to install the SZL or clock spring yourself and have a BMW dealer or specialist carry out the coding and calibration. The procedure takes only a few minutes. You will probably get charged for at least 30 minutes or an hour, depending on dealer policy.
Follow these steps to replace the steering angle sensor on a BMW.
Disconnect the battery and wait five minutes before you start working on the airbags and SZL module. Watch the video on how to perform this step.
Remove the airbag from the steering wheel. Use the access holes on the side of the steering wheel to release the airbag spring.
Disconnect airbag wires from the steering wheel.
Watch video on how to remove airbags on BMW 5-series E60.
Remove the bolt that secures the steering wheel to the steering column. You will need a breaker bar to get this bolt loose—Rember to counter-hold the steering wheel. Watch the video on how to remove the BMW steering wheel.
Remove clock spring from the SZL module. Remove bolts that secure the clock spring to the SZL module/steering switch unit. Watch the video on how to perform this step.
Remove wiper, turn signal, and cruise control switches if necessary. They are held in place with small bolts. Once the bolts are removed, you pull out the switches.
Install SZL / switch module in reverse order.
Reconnect the battery—Star the car. Turn the steering wheel all the way to the right then all the way to the left. Do this a couple of fo times.
Always clear the fault codes when you replace the SZL module on a BMW. Use a BMW-specific scanner to clear codes from the SZL module.
Carry out the steering angle sensor adjustment system function and calibration.
How to clean the BMW steering angle sensor
The steering angle sensor, which is integrated into the SZL module, is often the culprit.
The most common sign is that your traction control light/DSC and other warning lights will come on as soon as you start to drive and turn the steering wheel.
This problem is often caused by a dirty steering angle sensor that may have gunk built on it.
The good news is that it can be cleaned, and in most cases, it will fix the SZL problem.
There are two types of BMW steering angle sensors. The cleaning procedure depends on the type of steering angle sensor installed on your BMW.
Once you remove the SZL, you will tell which type is installed in your BMW. As a rough guideline, most BMW before 2007 had a potentiometer steering angle sensor. While 2007 and newer use optical sensors.
BMW Steering Angle Sensor uses Potentiometer
Up to around 2007, BMW used a Potentiometer to measure the resistance and calculate the steering wheel position. This steering angle sensor can be cleaned with Electronic Contact Cleaner.
BMW Steering Angle Sensor uses an Optical disc and sensor
The optical discovery time will build up a thin layer of dirt and oil. This layer can interfere with the optical sensor. When the laser sends light to the disk, the layer will block or diffract the light beam, in which case the steering wheel position can no longer be determined. Clean the steering angle sensor disk and reinstall it.
Only use a lint-free cleaning cloth. You can also use an eyeglass lens cleaner. Use a product similar to Meguiars Clear Plastic. Note that alcohol can cause a craze on plastic optical disks. It is better to use a product that is designed to clean discs and plastic.
Once you are done cleaning and putting everything back together, start up the car and turn the steering wheel clock to clock. Restart the car and drive it a short distance, and the lights should reset. If the lights remain on, read codes with a BMW scan tool. Carry out steering angle calibration and clear the codes.
The following part numbers are for reference only. Always verify the part number by removing your old SZL module or by calling the dealer. Note that part numbers will change if BMW introduced a new or upgraded steering switch unit.
Can I replace the clock spring without coding the SZL module?
The clockspring is part of the SZL module, and they are usually replaced as one unit. The clock spring can be swapped, but it is not a simple job.
I cleaned the steering angle sensor, and the DSc inactive keeps coming back. What could it be?
Check the alignment on your BMW. Bad alignment can trigger DSC light warning. Many shops will perform a free alignment check. Lowering the car can also trigger the DSC light. Also, check the battery on your BMW. If it is not holding a proper charge, replace it.
Does an SZL module need programming for the car?
Depends on the year and model. Typically SZL needs to be coded. VIN programming may be required in some cases. Call your BMW dealer to verify based on your vehicle's VIN.
Can you replace the BMW SZL module on your own?
Yes, the procedure is simple. If you have INAP or any BMW scan tool, you can perform coding and calibration of the steering angle sensor yourself.