Airbag Light On Due to Faulty Passenger Seat Mat Occupancy Weight Sensor

If the airbag light on your car is on, the most likely cause is a defective Passenger Occupancy Mat (also called Passenger Sensor, Passenger Seat Sensor, Passenger Weight Sensor, Occupant Detection Sensor, Airbag Weight Sensor,  OCS sensor, ODS sensor, FRS sensor). 

A sensor mounted in the front passenger seat senses when someone is sitting in the passenger seat. It is one of the most common problems with the airbag systems in most cars, including Mercedes, BMW, Hyundai, Kia, Honda, Audi, Toyota, Chevy, Subaru, Nissan, VW, etc. 

Learn what the passenger seat sensor does. Before you decide to bypass the passenger seat sensor, use an airbag scanner to verify that the airbag light is due to the seat weight sensor. If yes, call your dealer to check if there is a recall on these problems. Most car manufacturers will replace the passenger seat sensor free of charge even if they are out of warranty. Check with your local dealer. 


airbag weight sensor

Airbag light illuminating on the dash and message on the screen about a malfunction of the restraint system. 

  • Airbag light on
  • The airbag light won't' go off.
  • Message: Restraint system defective
  • Front Pass. Restraint System Fault
  • Restraint Sys. Malfunction/Defective
  • Fault in Pass. Restraint System Affecting Airbag

What is Passenger Occupancy Sensor?

passenger sensor

Passenger Occupancy Sensor, also known as Weight Sensor, Seat Mat, Passenger Occupancy Mat, is installed under the passenger seat's seat cushion.

Its purpose is to send a signal to the airbag module if an adult is sitting on the passenger seat. This will allow the airbag module to deploy the passenger airbag in case of an accident. It is also used to detect if a child or car seat is on the front passenger to not deploy the airbags since if an airbag deploys, it can injure the child.

To verify that the problem is the passenger seat mat, you can use an airbag scanner to read the fault codes via the diagnostic port located under the dashboard on the driver's side. 

What is Seat Belt Bypass, Emulator?

passenger warning light

A passenger seat mat bypass simulates an adult sitting on the passenger seat, ensuring that the airbag always deploys in an accident. The airbag control unit (SRS) will treat the passenger seat as if they are always occupied by an adult, even if a child or no one is sitting there.

The emulator sends the same signal to an airbag control unit as that sent by a mat while the passenger is present.

Passenger mat bypass simulates that your passenger seat is occupied. Therefore the passenger airbag on the passenger side will deploy in case of an accident even when nobody is sitting on the passenger seat.

Here are a few important facts to understand with regard to installing a passenger sensor bypass. 

  • The passenger airbag will always deploy in case of an accident, even if there is no one sitting or if a child is in the front passenger seat.
  • It may be illegal to modify the restraint system. Check the laws in your country.
  • Do not have children's seat on the front passenger seat. Front passenger airbags will deploy if you get in an accident, and it can injure your child.
  • If you sell your car, you should disclose to the buyer if you have installed a passenger seat mat bypass.

How does the airbag module "see" the bypass emulator.

  • Seat Status: Occupied
  • Seatbelt Status: Fastened
  • Seat Occupancy Sensor: Installed, Working

Once you successfully install the passenger occupancy sensor, you may notice the seat belt reminder chime. This is a sign that the installation of the bypass went well. The car is detecting the presence of an adult in the passenger seat. To disable the seat belt warning, you will need to install a seat belt warning emulator.

Even after installing a passenger seat bypass, which is not recommended, the airbag light may still stay on. You will need to use an airbag scanner to read and, if needed, clear the codes via the OBD2 port under the dashboard. 

By  YOUCANIC Automotive Experts

Published on: Monday, January 13, 2020.
Updated on: Thursday, December 31, 2020