Modern BMWs are plagued with a faulty airbag light indicator regularly rearing its ugly head thanks to a faulty passenger seat mat sensor. It's a frustrating problem, and the only way to properly rectify the solution is to replace the seat mat with a new part.
Many owners opt to fit what is known as a BMW seat mat occupancy airbag sensor malfunction bypass, but before venturing down this route, it's worth investigating if BMW will perform a dealer recall fix on your vehicle. To do this, simply phone your local dealer, and upon divulging your vehicle reg or VIN number, they will be able to tell you if you are eligible to have the problem rectified by them, free of charge.
If a recall is not an option, then it might be necessary to install a bypass module. (As with all car modifications, this route should only be considered with full knowledge and understanding of the legal implications of such an installation.)
But what is a BMW seat mat occupancy airbag sensor malfunction bypass?
Well, a seat mat bypass exists to simulate the presence of an adult passenger in the front seat. Primarily, its main function is to engage the airbag in the correct circumstances and ensure that in the event of an accident, both airbags are effectively deployed. A seat mat emulator also allows the clearing of any fault codes that may have occurred, thus turning off the airbag warning light on the dashboard.
It's worth noting that the installation of the passenger weight sensor emulator does not bypass the passenger airbag, if correctly installed, the airbag still deploys in an accident, providing the rest of the restraint system is in good working order.
It is crucial to note that the installation of a BMW passenger seat emulator will result in the airbag always deploying, regardless of the occupancy of the seat. For this reason, children in car seats or on booster seats must not be allowed to sit in the passenger seat. If the airbag were to activate with children or toddlers in the seat, fatal injuries could be incurred.
How do I know if the airbag sensor is not working correctly?
There are a variety of symptoms presented by an inoperational passenger weight sensor. Typically, the airbag light will be constantly illuminated, accompanied by one of the following error messages:
- Passenger Restraint System Error
- Front Pass. Restraint System Fault
- Driver Restraint System Malfunction
- BMW Airbag Light On
- Restraint Sys. Malfunction/Defective
- Fault in Pass. Restraint System Affecting Airbag
- Fault Codes: 93C1, 93C2, or 93C3
- Pass. restraint system waring on iDrive
- BMW Passenger Occupancy Sensor Failure
DISCLAIMER
The installation of a passenger seat mat emulator could affect the protection offered by your car, it is not an advised solution and should be undertaken with caution.
Be aware that in some countries, it is illegal to tamper with this safety system. You may be responsible for any consequences occurring from the installation of any seat mat emulator, this liability continues even after you have sold the car.
Instructions for installing passenger seat mat emulator/bypass
Step 1:
Start the engine and bring the passenger seat as far forward as it will go. Tip the passenger seat to its most forward position.
Step 2:
Turn off the engine, removing the key from the ignition.
Step 3:
Look under the passenger seat for the seat mat sensor and find the sensor wires. The plug is usually positioned right under the seat, although some vehicles might have the connector under the seat cushion itself. The occupancy mat sensor is attached to the seat mat control module.
Step 4:
Under the passenger seat there will be either a 2 or 3 wire connector. If a 2 wire connector is installed, you should find a white and blue casing, if your BMW has a 3 wire connector, you should find white, red and brown wires. The connector itself should have 4 pins. Don't worry if the colours do not match, there is some variety between models. If your vehicle is an X3 or Z4, you won't find a connector, instead, you will need to cut the wires and solder the emulator into place.
Step 5:
Unfasten the connector and unplug the existing seat mat circuitry.
Step 6:
Plugin the new seat mat bypass emulator.
Step 7:
Start the vehicle
You should now find that the airbag light has been extinguished.
Now the airbag bypass has been installed, the car will continue to notify that the passenger seatbelt isn't being worn, even if no one is sitting in the seat.
To solve this problem it is necessary to install a seat belt emulator.
