Home2007-2013 3 Series (E9x)BMW E90 Passenger Seat Occupancy Sensor Repair- 2007-2013 3 Series

BMW E90 Passenger Seat Occupancy Sensor Repair- 2007-2013 3 Series

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Repair Summary
This article gives detailed instructions on bypassing the passenger seat occupancy sensor in 2007-2013 3 series vehicles (E9x). Even though we used a 2011 335i to perform this repair, this article can be applied to any 2007-2013 3 series with minor modifications to the repair steps.

The BMW E90 passenger seat occupancy sensor is a very expensive part that can be easily bypassed.

One of the most annoying issues that owners of 2007-2013 BMWs have to deal with is a passenger-side seatbelt reminder chime and a warning light that remains active when the seat is not occupied. Most owners are reduced to driving around with the seatbelt buckled in an empty passenger seat, or even overriding the system with a seatbelt "blank". Compounding the issue is the fact that replacing the faulty seat occupancy sensor mat (which is causing the issue) is a difficult and extremely expensive procedure. A new BMW E90 seat occupancy sensor mat can cost close to $1000...just for the part itself.
The good news is there is a less expensive solution - installing a seat occupancy sensor emulator and a seatbelt chime bypass device. A seat occupancy sensor emulator is an electronic device that plugs into the passenger seat's wiring harness in place of the defective mat. Its job is to imitate a seat occupancy mat sensor that has been triggered by a passenger - in other words, it sends a signal to the vehicle's control module that the passenger seat is occupied...removing the seatbelt and airbag warning lights on the dashboard. Simply put, it does the same job as buckling the seat belt with no one in the seat. The seatbelt chime bypass device also connects to the wiring harness - it silences the seatbelt warning chime.
The BMW E90 3 series uses two devices to bypass the passenger seat seatbelt and airbag warnings - the mat emulator which removes the warning lights and a chime bypass that silences the seatbelt warning chime. Both of them must be installed to complete this repair.
Performing a BMW E90 occupancy sensor bypass by installing an emulator is a fairly easy repair, even for the home mechanic. It only takes about 20 minutes and can easily be done in your driveway or garage. The BMW Repair Guide strongly recommends disconnecting the battery after the seat is removed and prior to disconnecting the wiring harnesses - this will prevent causing an inadvertent short which can damage sensitive electronics. We give full step-by-step instructions below, including a video and parts list for your convenience.
View the video version of this repair.
View the detailed parts diagram for this repair.
Includes detailed part diagrams, part numbers and links to purchase all of the required components needed to complete this repair.
Before starting this repair, you must have the following required parts.
Fits all BMW E9x vehicles (2007-2013 3 Series)
Tired of driving around with the passenger seat belt buckled because the seat belt warning light and chime won't go off? A seat occupancy mat emulator is a simple-to-install device that will immediately fix the issue.
Repair Steps
Section 1 - Installing the BMW E90 passenger seat occupancy sensor emulator
The passenger seat occupancy sensor in BMW E9x models is actually a mat located within the seat cushion. In order to bypass the passenger seatbelt warning light and chime, both a mat and chime bypass device must be installed. The BMW Repair Guide strongly recommends disconnecting the negative battery cable on the vehicle before starting this repair...this will prevent inadvertently causing a short which can damage sensitive electronics.
  1. In order to properly install the seat mat emulator and seatbelt chime bypass device, the passenger seat mounting bolts need to be removed. This will allow the seat to be tilted back, offering easy and clear access to the wiring harnesses.
  2. Use a T50 torx bit to remove the front and rear mounting bolts. Tilt the seat back so the wiring harnesses can be accessed.bmw e90 seat occupancy sensor repair - Remove the front and rear seat bolts bmw e90 seat occupancy sensor repair - Tilt the seat back so the wiring harness can be accessed
  3. Locate the seat occupancy mat connector. It is clipped to a plastic rail underneath the seat as shown below.Locate the seat mat occupancy sensor connection
  4. Disconnect the seat mat occupancy sensor. Plug the seat mat emulator in its place. Make sure the switches are set correctly: North America - switch 1 on, 2/3 off.  All other countries switch 1/2/3 off (please see our video above for more information).Unplug the seat mat occupancy sensor and plug in the emulator in its place bmw e90 seat occupancy sensor repair - Make sure the emulator dip switches are set correctly
  5. Next, locate the main seat wiring harness. It has a yellow connector. Disconnect the wiring harness by pulling the plastic release up.bmw e90 seat occupancy sensor repair - Locate the yellow wiring harness connectorRelease the wiring harness by raising the plastic release Pull the wiring harness plug apart
  6. Using a small flat blade screwdriver, remove the two white connectors from inside the wiring harness plug as shown below.
  7. Locate the red and black wires in the second smaller connector...these control the seat belt warning chime. Using a metal pick, release the wire connectors and pull them free. Install the wires from the door chime bypass by pressing them in until they click in place.Locate the red and black wires in the smaller connector bmw e90 seat occupancy sensor repair - Use a metal pick to remove the red and black wires
  8. Reconnect the battery and test the emulator before reassembly.bmw e90 seat occupancy sensor repair - Remove the black and red seat chime wires from the connector Insert the seat chime bypass wires into the connector bmw e90 seat occupancy sensor repair - insert wires until they click into place bmw e90 seat occupancy sensor repair - The seat belt warning chime bypass installed
BMW E90 Passenger Seat Occupancy Sensor Repair Finished

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