By YOUCANIC on Apr 4, 2019
Is your BMW airbag light on and won't turn off? When your BMW airbag light stays on it means there is a problem with the Supplemental Restraint System (SRS) and the airbags may not deploy if you get into an accident.
In this article, you will learn how to troubleshoot BMW airbag light yourself using scanners such as Foxwell NT510 for BMW and Carly adapter. You will also learn about some of the most common problems that can trigger BMW airbag light.
Symptoms that BMW drivers notice when there is a problem with the airbag system.
Follow these instructions to read and clear codes from the airbag control unit on a BMW. The instructions apply to all 2002 and newer BMWs including 1-Series, 3-Series, 5-Series, X1, X3, X5 etc.
In this video, you will learn how to read and clear BMW airbag light using Carly for BMW.
Without reading the codes, there is no easy way to know the reason why BMW airbag light is on.
With that said, there are a few common causes and trouble spots that often trigger BMW airbag light. We don't recommend replacing parts without pulling the airbag codes first.
The #1 common issue causing BMW airbag light to come on is due to a defective passenger seat weight sensor (also referred as the occupancy sensor, child sensor, passenger mat, seat sensor pad).
The sensor is installed under the passenger seat cushion and detects if the passenger is over a certain weight. If the person is not over the weight limit (ex. a child), the passenger airbag will not deploy in case of an accident because it can cause injuries to the child. This sensor fails very frequently and is often the culprit.
Usually, if the seat occupancy sensor is defective on your BMW, you will get a warning on your iDrive screen with a message stating that there is passenger airbag problem or passenger airbag off.
To fix this problem, it requires the removal of the seat and seat cushion. At the dealer, this problem will cost you $500+. If you have DIY skills, you can replace the passenger seat sensor yourself. A replacement passenger seat mat sensor can be purchased online for under $200. Check out these listing of BMW Passenger Weight Sensor. To replace the passenger weight sensor yourself you will need a few basic tools and about two hours.
Many BMW owners install what is called a BMW Passenger Sensor Bypass. It tricks the airbag system to think that the sensor is working properly.
It is important to understand that if you install a BMW weight sensor bypass and get in an accident the passenger airbag will deploy even if there is no passenger or a child sitting in the passenger seat.
In some countries, it may be illegal to modify the restraint system. Perform this modification at your own risk!
The airbag light on BMW may stay on if you replace the car battery or jump-start a dead battery.
An under-voltage fault (supply voltage) code is stored in the SRS control unit.
This happens because either the old battery was no longer providing the required voltage (voltage dropped under 12 volt) or you disconnected the battery while the key was in the ignition. There will be stored codes in the airbag module but they can be cleared using a BMW airbag scan tool.
Another reason why the airbag light may stay on is the seat belt buckle defective. Inside the seat belt buckle is a small switch that can fail. When you start the car, it can detect that you are in the seat but the airbag control unit may not be getting a signal from the seat belt buckle.
Try pressing the seat belt buckle a few times and check if the airbag light turns off. In some cases, the seat belt may not latch when inserted into the buckle.
A common problem that triggered airbag light is BMW seat belt pre-tensioner. The pre-tensioner is used to tighten the seat belt in case of an accident. If the driver or passenger pre-tensioner fail, it will trigger the airbag light.
A BMW pre-tensioner takes about one to two hours to replace. When you read SRS fault codes you will get fault codes pointing to the pre-tensioner.
If your BMW was involved in an accident, the airbag light will stay on. Even if you replace the airbag that blew, the light will stay on. Crash data is stored in the airbag control unit, and cannot be cleared even with a BMW airbag scan tool.
To fix this problem, you have two options. You can replace the airbag control unit on your BMW which can get very expensive.
A cheaper alternative is to send your BMW airbag module to facilities that can Reset BMW Airbag Control Unit. They will erase the crash data from your BMW airbag computer and send the unit back to you. This solution does not require the computer to be re-programmed.
Just plug and play. It is a lot cheaper than replacing the airbag module and installing a new unit.
If the airbag light is staying on and your horn doesn't work, it is most likely that you have a bad clock spring. Clock spring is installed in the steering column right behind the steering wheel. It requires the removal of the steering wheel to be replaced.
On certain BMW such as E36 it is integrated into the steering wheel, which means it requires the replacement of the steering wheel as well. As your BMW clock spring (slip ring) starts to fail you may start hearing a strange sound (ex: rubbing sound) coming from the steering wheel as you turn it.
If you are working near airbag sensor and you happened to unplug the sensor while the key is in the ignition and the car is powered, you will trigger the airbag light. Always disconnect the battery when you change a window regulator or replace a front bumper.
To move the window up and down to pull out the regulator, reconnect the airbag sensor before you turn the ignition on. Otherwise, there will be a fault code stored. The good news is that there are several BMW airbag scan tools to help you clear the codes yourself.
Electrical wires under the driver or passenger seat may get damaged or the electrical connection may get loose. Move the seats back and forth and rescan for codes. If the fault codes change from present to store, the problem is one of the electrical connectors.
Inspect the connectors and wires to make sure they are not exposed.
Related possible problems that can trigger the SRS light on BMWs include:
Works on older BMW made from 1994-2003.
One of the cheapest BMW airbag scan tools. Comes with the 20 pin connector. It works on older BMW. Vehicle coverage is 1994 to 2003 BMWs.
BMW has issued several recalls related to airbag problems. If your car has been affected by the recall, a BMW dealer will fix the airbag problem free of charge. Your BMW doesn't have to have an existing warranty to be covered by a recall.
To check if your car has been affected by BMW airbag recall can call your dealer. Another method to check if a BMW has been recalled for airbag problems is to enter your VIN number and lookup BMW recalls by VIN. Or search for BMW airbag recalls by make and model here.
Diagnosing BMW airbag light at the dealer will cost you at a minimum one hour labor. Which means $120+ in most places. BMW independent repair shops may be willing to scan the codes and only charge half an hour. To fix the problem will cost you even more.
To diagnose BMW airbag light yourself you will spend in average $100 to purchase a scanner that can read BMW specific codes. Once you get the codes, you can decide if you want to fix the problem yourself or have a mechanic fix it for you. At least you will have a better understanding of what's wrong with your BMW.
It depends. For example, if BMW airbag light is on because of a fault with the seat belt buckle, the airbags will deploy if you get into an accident. If the airbag light is on, because there is no communication with the airbag control unit, or one of the airbag sensors is defective, there is a high chance that the airbags will not deploy in case of an accident. Weather BMW airbag deploy or not depends on the nature of the problem. Note that if the airbag light is on, there is a chance that all airbags may deploy even during a minor accident.
While airbag light on, does not affect drivability, you may not be protected in case of an accident. It is not advised to drive a BMW with the airbag light on. The airbags may not work if you get in an accident.
No. These are codes stored in the airbag control module. A BMW specific tool that can reset the airbag is required to reset the light.
Make sure to use a BMW specific scanner. Generic OBD2 code readers are not capable of reading BMW airbag codes.
If the airbag light on your BMW is flashing it means that the airbag control unit is either defective, not communicating or misconfigured.
If the airbag light comes on and off, it is often caused by a loose wire or contact. For example, the micro-switch in the seat belt buckle may get stuck. Another example would be a clock spring starting to wear no providing connection to the driver's airbag. Here is a quick way to check if the problem is the clock spring. Next time you get a warning message related to the airbag system, try to see if the horn is working. If the horn has stopped working, the problem is the clock spring. Don't rule out the clock spring if the horn works. It may still be defective. Read codes from the airbag module.
No. If the problem isn't fixed, you can NOT clear BMW airbag codes. You can clear the codes from airbag module but they are reset right away. If you clear BMW airbag codes, as soon as you restart the car, the airbag light will turn on again.
No. Generic OBD2 code readers can not clear BMW fault codes. You will need a scanner that can read and clear BMW specific fault codes. Read this article on Choosing the best scanner for BMW.
It depends on the sate. In most states, you will pass. In a few states, you can't because they require the airbag light to be off. The airbag warning light has a different computer (SRS Control UNit) and does not store a code on the Engine Control Unit ECU. When a car is taken in for inspection, state inspection stations only scan for codes in the ECU.
It is not uncommon for the airbag light to come on if you cleaned the car. Often owners may move the front driver or passenger seat too far forward stretching the airbag wires, unplugging the connector under the seat. Check the wires and plugs under the front seats. Make sure they are secure. The light may not turn off even if you reconnect the wires because a code is stored and will often require a BMW airbag scan tool to be reset.