BMW Airbag Restraint System Malfunction

On BMW vehicles, a Restraint System Malfunction warning message pops up, and the airbag light (SRS) turns on to warn the driver that the airbags are not working properly and may not deploy in case of an accident. The most common problems that cause airbag light and restraint system malfunction warnings on a BMW are low battery voltage or faulty passenger occupancy sensors (mounted under the passenger seat).

A BMW airbag restraint system malfunction refers to a problem with one or more components of the airbag system in a BMW vehicle. This can include issues with the airbag sensors, the deployment mechanisms, or the airbags themselves. A warning light will typically illuminate the dashboard if a malfunction is detected, and a diagnostic trouble code (DTC) will be stored in the vehicle’s onboard computer. Depending on the specific problem, the airbags may not deploy properly in the event of a crash, which can increase the risk of injury. It is important to have the issue diagnosed and repaired as soon as possible to ensure the safety of the vehicle’s occupants.

Symptoms

Most BMW owners will get one of these warnings when there is a problem with the airbags and restraint system.

• 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.

Common Problems

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. The airbag warning light will come on if these sensors are not working properly.
• 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 properly.
• 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.

It’s important to have the vehicle inspected by a certified BMW technician to diagnose and repair the issue to ensure the safety of the vehicle’s occupants. Other common problems that trigger BMW restraint system malfunction.

• 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

Troubleshooting

Check Airbags

Airbags are restraint device that deploys 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 that connect to any of the 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 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 handled properly.

Seat Belt

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

Below you will find instructions on reading fault codes from the BMW SRS module. For this procedure, you will need a BMW scanner.

The YOUCANIC Full System Scanner can read and clear fault codes through every control module of your BMW vehicle.

1. Park your BMW and set the parking brakes.
2. Locate the diagnostic port under the dashboard.
3. Turn on the ignition but do not start the engine. Please turn on the scanner and allow it to communicate with the vehicle.
4. Select BMW from the main menu, then your particular model.
5. Select Control Units next. Select SRS Airbag Module
6. Select Read Fault Codes. Watch the following video to learn more.

Restraint System Warning Messages

This is a list of warning messages that may display 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.

Conclusion

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 ensure the protection of the vehicle’s occupants.

Frequently Asked Questions

We hope you find the BMW Airbag Restraint System Malfunction guide helpful. Check these troubleshooting and repair guides for more help on your BMW.