4 Reasons Why BMW Passenger Restraint System Malfunction

A water leak, low battery voltage, and airbag and seat sensors malfunctioning could cause the passenger safety system malfunction warning to appear on the dashboard. The airbag system is a critical system devoted to passenger safety so do not ignore the warning.

The causes of a passenger restraint system malfunction

When there is an issue causing the passenger restraint system to malfunction, a warning will appear on the BMW dashboard. The warning will state:

Passenger restraint system fault and passenger-restraint system affecting airbag, belt tensioner or belt force limiter.

Unlike other warnings, you should never ignore a passenger restraint system warning. This system controls the airbags.

If there is an issue and you get into a collision, the airbags may not deploy. That means you or any passengers in your vehicle will suffer more injuries than if the airbags did deploy.

Water leak damages components

Water can get anywhere and everywhere in the vehicle. Water from the engine could leak out. water can wreak havoc on the passenger restraint system.

So, if any part has been damaged, get them replaced ASAP. Water damage is good at destroying metal components, so expect to have to replace the parts.

Low battery voltage

If enough electricity is not getting to the passenger restraint system, then the system cannot function. The sensors will not have enough power to gather data.

Also, the airbags will not deploy with the same Force it’s supposed to. So, where’s the cause of a low battery voltage? It could be bad wiring or a bad fuse.

Airbag sensors are not working

If the airbag is not working or its sensors are not putting the correct data, don’t ignore these issues. You may have to get the airbag and the airbag sensor replaced.

Replacing an airbag sensor is not cheap. The sensor by itself can be anywhere from 50 to $300. The total cost of replacing a sensor can rise to $600.

The sensor inside the seat is not working

In a BMW, the passenger airbag sensor is underneath the passenger and driver seats. The passenger restraint system needs multiple sensors in different parts of the vehicle.

It makes it easier to detect a collision. If the sensor inside the seat doesn’t work, it’ll be harder for the system to know when to deploy an airbag.

What is the passenger restraint system?

The passenger restraint system will keep you safe in the event of an accident. This system is made of sensors, wiring, and airbags.

Please note that the passenger restraint system works with the BMW seat belt. Airbags are not meant to be your sole protection in the event of an accident. 

If you are not wearing your seatbelt when you get into a crash, you could be seriously injured.

When the airbags work in a BMW and the driver wears their seat belt, they’ll be far more protected than if they only had one of the other.

How to find the Passenger restraint system fuse?

Navigating through the maze of fuses in the passenger restraint system is a bit tricky. But you can do it yourself. You don’t need any special tools. 

If you suspect the passenger restraint system warning is on because of a computer glitch or sensor glitch, then replacing the fuse can solve the problem. 

It may also save you hundreds of dollars in mechanic repair costs. You can also use this guy to help you replace a burnt-out fuse.

Here’s how to find the burnt-out fuse

  • Turn on the vehicle and the warning should appear on the dashboard. Leave the vehicle on and open the trunk.
  • Look for a schematic that outlines which fuses go to which compartments and components in the car. This is the list of fuses located in or behind the glove box.
  • Look for the airbag component and look for its fuse number.
  • Then go to the bottom and you will see small boxes titled fuse number and amperes.
  • Find the fuse number and the number below in a column is the fuse you should look for.
  • Now go to the fuse box
  • Open the fuse box and smell the area. This may sound strange but sometimes you can smell if a fuse is burnt out.
  • Look for the fuse with the number of amperes. If the amperes number is 20, then that’s you should say 20.
  • Remove the fuse and inspect it. If the fuse looks burnt out, then replace it. Although, it will not always look burnt out. If you think the fuse is the issue, replace it with a new one. 
  • Replace the fuse with a new fuse and be sure to mark that fuse with the same number as the one you pulled out.

Navigating the fuse box is difficult and there are many little fuses involved. But don’t feel discouraged and take your time.

If you have a mechanic friend, it is best to ask for their advice.

How to know if there is an issue with a passenger restraint system

If the warning light does not turn on, that does not mean that everything is working as it should. Computer systems can’t catch everything so there could be a problem developing and you wouldn’t know it. 

When it comes to the passenger restraint system, there are two critical signs to watch for. If you see either of these two signs, then there’s a problem with the system.

The airbag light turns on every time you turn on your vehicle. This light alerts the driver so they will know there’s an issue with the airbag.

If your BMW says there is a sensor issue, then it could be a sensor attached to the passenger restraint system. It is easy to replace a sensor.

However, it is hard to test every sensor to find out which one is the problem. There are many sensors, so you’ll have to be patient.


If a sensor is burnt out or damaged, the owner of the BMW can buy a new fuse for less than $10. Low battery voltage issues are harder to fix so hire a mechanic.

It’s easy to replace the passenger restraint system fuse if you know how to look at the schematic and find the fuse number.

  • Eric Williams

    I'm the founder of Daily Car Tips. I wrote articles in the automotive industry for more than 10 years, published in USA and Europe. I love sharing my knowledge and insights with fellow enthusiasts. Join me on this journey as we explore the exciting world of cars together!