Restraint System Malfunction warning messages often appear on BMW vehicles along with an airbag light (SRS) illuminated to warn the driver about a malfunction of the airbags with potential consequences that the airbags may not function correctly in case of an accident. The most common issue leading to the failure of the BMW airbag light and restraint systems is a faulty passenger weight sensor under the front seat. Our frequent experiences are related to low battery voltage and faulty passenger occupancy sensors (mounted under a passenger seat).
What is a BMW airbag restraint system malfunction?
A malfunction of the airbag restraint system, including one or several critical features of the airbag system of a BMW, can be understood as an issue with sensors, deployment devices, or airbags. A light will usually be illuminated on the instrument cluster notifying you about the malfunction, and additionally, a trouble code (DTC) will be stored in the vehicle computer. The airbags may fail to inflate correctly, resulting in more injuries than if the airbag had functioned properly. The malfunction must be diagnosed and replaced as early as possible to ensure the safety of the vehicle’s occupants.
Most BMW owners will get one of these warnings when there is a problem with the airbags and restraint system.
Access Factory Repair Manuals
The YOUCANIC Pro Manuals offer OEM Factory Repair Manuals with detailed steps and illustrations, comprehensive wiring diagrams, torque specifications, and access to technical service bulletins and OEM service information, mirroring dealership manuals.
- The airbag light stays on
- Driver Restraint System Malfunction error
- Passenger restraint system malfunction warning.
- Restraint System Faulty
- Pass. Restraint System fault on the dashboard
Get your BMW diagnosed as soon as possible, and continue to wear the seat belt.
Several common causes can trigger the BMW airbag warning light, some of which include:
- Faulty airbag sensors: These sensors detect impact and send a signal to the airbag control module to deploy the airbags. If a sensor is malfunctioning, the warning light will be illuminated.
- Wiring issues: Damage or corrosion to the airbag system’s wiring can prevent the airbags from deploying properly.
- Occupant detection sensor malfunction: Some BMWs have sensors that detect the presence of passengers in the vehicle. If these sensors are not working correctly, the airbag warning light will come on.
- Control module failure: The airbag control module is responsible for deploying the airbags in the event of a crash. The warning light will be illuminated if the module is not functioning correctly.
- Low battery voltage: A low battery can affect the airbag system’s performance. The warning light will come on if the voltage is too low.
Since the malfunction is a safety feature in the vehicle, the vehicle must be taken to a certified BMW technician to diagnose the issue and repair the vehicle accordingly to avoid placing the occupants in harm’s way—additional frequent causes of the BMW restraint retraction system malfunction include:
- Fault in the airbag module
- Defective seat belt tensioner
- Belt force limiter
- Low battery voltage
- Defective clock spring
- Passenger occupancy sensor
- Wire harness
- Water damage
Airbags are restraint devices that deploy only during a severe collision. Depending on the model, there are front, side, and curtain airbags. The steering wheel and the passenger-side dashboard hold front airbags.
These are activated in a frontal impact to minimize head and chest injuries. The side airbags are installed in front seats to protect passengers during side impacts and vehicle rollovers. Airbags installed on the curtain serve a similar function as side airbags and help reduce the risk of injury from broken glass. They are located between the A and C pillars.
An airbag previously deployed will activate the restraint system malfunction warning light. But a more common issue is the wire harnesses connecting to any airbags. Airbags can get damaged during a minor accident or previous repair work.
Airbag / SRS Module
The supplemental Restraint System (SRS), also known as the airbag module, controls the restraint system. It uses impact sensors to determine the severity of a collision.
When the system detects sufficient deceleration, it takes action within about 20 milliseconds. If the impact force is low, the control module may deploy the seatbelt pre-tensioners only and display restraint system malfunction on the dashboard.
If the impact force is high enough, the airbags will also deploy at about the same time. A signal ignites a chemical reaction, rapidly expanding nitrogen gas, inflating the airbag within about 30 milliseconds.
Passenger Occupancy Sensor
Besides these features, most BMWs from 2003 onwards have a system that monitors when a passenger is on the seat and their weight.
The seat occupancy sensor is, by far, the most common failure point. This sensor is an electrical mat installed into the base of the passenger seat. As it carries the entire weight of the passenger, it usually fails over time. It begins as a minor issue but gets worse over time.
Although emulators can solve this problem, they always make the passenger airbag active. Although time-consuming and costly, the best solution is to replace the sensor.
Battery Safety Terminal (BST)
Cars with a battery safety terminal, or BST system, can have an issue with a damaged BTS cable. Usually, this happens during a battery change and causes a malfunction of a restraint system. Follow this guide to learn how to replace the BMW BST terminal.
Connector / Wire harness
Another possible issue is a loose or broken seat connector. They are found at the bottom side of both the driver and passenger seats. Foreign objects pushed under the seat can easily damage these connectors, especially if the seat is moved back and forth frequently. Other components, such as airbags or seat belt tensioners, rarely fail. However, they can get damaged or activated during assembly or disassembly if not appropriately handled.
Seat belts prevent sudden forward movements and ensure passengers are in the correct position for airbag deployment. Seat belts have pre-tensioners, which tighten the seatbelt across the passenger’s lap and chest to prevent excessive forward movement. Also, a load limiter relaxes the tension of the seatbelts in a controlled manner to reduce the pressure on the passenger’s chest.
How to Diagnose BMW Restraint System
The YOUCANIC Full System Scanner can read and clear fault codes through every control module of your BMW vehicle.
- Park your BMW and set the parking brakes.
- Locate the diagnostic port under the dashboard.
- Turn on the ignition, but do not start the engine. Please turn on the scanner and allow it to communicate with the vehicle.
- Select BMW from the main menu, then your particular model.
- Select Control Units next. Select SRS Airbag Module
- Select Read Fault Codes. Watch the following video to learn more.
Restraint System Warning Messages
This list of warning messages may be displayed on the dashboard.
- Driver restraint system malfunction. Continue wearing a safety belt. Consult the nearest service center.
- Passenger restraint system. Fault in the airbag, belt tensioner, or belt force limiter. Continue wearing a safety belt.
- Pass. Restraint system. Fault in a passenger restraint system affecting airbags.
- Carefully drive to the closest service center. The passenger restraint system is limited—an increased risk of injury in case of a collision. Continue wearing the safety belt.
- Pass Restraint System – Fault in passenger restraint system affecting airbag, belt tensioner, or belt force limiter. Continue to wear the safety belt.
- Passenger restrains system. Malfunction. Continue wearing the safety belt. Consult the nearest service center.
Airbag restraint system malfunction is a prevalent issue faced by BMW owners. This can occur for various reasons, such as low battery voltage or malfunctioning passenger occupancy sensors. Though common, this problem can pose a significant safety risk and should be addressed as soon as possible to protect the vehicle’s occupants.
Frequently Asked Questions
What are the possible causes of a BMW airbag light?
Fault in the airbag module
Defective seat belt tensioner
Belt force limiter
Low battery voltage
Defective clock spring
Passenger occupancy sensor
How can I diagnose the BMW Restraint System?
The fastest way to diagnose a BMW Restraint System is by scanning it using an OBD-II Scanner.
Is it OK to drive with the airbag light on?
Yes. because when the light is on, the airbag light is deactivated. But for your safety, it is better to fix the problem as soon as possible.