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Front Seat Belt Buckle Replacement
 
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Pelican Technical Article:

Front Seat Belt Buckle Replacement

Nick Czerula

Time:

1.5 hours

Tab:

$100

Talent:

***

Tools:

Socket set, flat-head screwdriver

Applicable Models:

BMW E46 3-Series (1999-06)

Parts Required:

Seat belt buckle

Hot Tip:

Be sure wire harness is properly routed and attached as it was before.

Performance Gain:

Remedy fault code for seat belt pretensioner

Complementary Modification:

Clean carpet and interior beneath seats

Front seat belt buckles in BMW E46 models are equipped with pyrotechnic automatic pre-tensioners. The pyrotechnic device has an explosive charge, which is triggered by the airbag (MRS) control module in case of sudden deceleration such as a car crash. Once triggered the device cinches up the seat belt by 55mm (about 2 inches). 

The seat belt pre-tensioner can fail over time and will set a fault code in the airbag control module. If a fault code is set, the airbag warning light will illuminate. To replace this part you have to remove the front seat to access the fastener and wiring harness. If your airbag light is on, you will need a code reader or scan tool to determine what fault code is stored. If you find you have a pre-tensioner fault code, this is a good place to start. You will also need to clear the fault code once the part is replaced; simply replacing the part will not turn off the airbag warning light.

In this tech article, I combined the procedures for front seat belt buckle and front seat removing, as they are so closely related. 

The pyrotechnic pre-tensioner in the seat belt buckle mechanism poses a hazard if not handled carefully. The front seat belt buckles are bolted to the inside of each front seat. If you aim to remove either front seat, disconnect the negative battery terminal and insulate the end with electrical tape to prevent accidental reconnection.

Interior trim pieces in BMW E46 cars are often made of preformed hard plastic. Plastic clips or metal screws are used to hold them in place. To avoid marring the trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out trim panels, switches or electrical accessories.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you are working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Move seat all the way forward and up to highest position.
Figure 1

Move seat all the way forward and up to highest position. Then working at outer seat rail, remove seat belt mounting bolt (green arrow). Raising the seat to highest position allows access to this fastener, otherwise it is blocked by the rear seat trim.

Next, remove two 16mm seat mounting bolts from rear seat rails (green arrows).
Figure 2

Next, remove two 16mm seat mounting bolts from rear seat rails (green arrows).

Move seat to furthest back and lowest position.
Figure 3

Move seat to furthest back and lowest position. Then lever off trim pieces using a flat-head screwdriver (green arrows).

This photo shows how to lever off trim pieces using a flat-head screwdriver.
Figure 4

This photo shows how to lever off trim pieces using a flat-head screwdriver.

Next, remove two 16mm seat mounting nuts from front seat rail (green arrows).
Figure 5

Next, remove two 16mm seat mounting nuts from front seat rail (green arrows). Disconnect battery negative cable. See our tech article on battery installing and connecting.

Lift front of seat up and tilt back; let seat back rest on rear seat.
Figure 6

Lift front of seat up and tilt back; let seat back rest on rear seat. Then working under front seat, disconnect seat electrical connectors by levering locking tab (green arrow) out and pulling connector apart.

Cover seat rail with a fender cover, then pull seat out through door opening.
Figure 7

Cover seat rail with a fender cover, then pull seat out through door opening.

With seat on floor, disconnect seat belt pretensioner electrical connector by levering up one side and pulling up on other (green arrow).
Figure 8

With seat on floor, disconnect seat belt pretensioner electrical connector by levering up one side and pulling up on other (green arrow).

Remove wiring harnesses (green arrow) from pretensioner buy pulling mounting bracket off with harness attached.
Figure 9

Remove wiring harnesses (green arrow) from pretensioner buy pulling mounting bracket off with harness attached.

Then remove T50 Torx seat belt buckle fastener (green arrow).
Figure 10

Then remove T50 Torx seat belt buckle fastener (green arrow).

Remove seat belt buckle with pretensioner from seat.
Figure 11

Remove seat belt buckle with pretensioner from seat. This is a good chance to clean the side of your seat. There may be stains or a bunch of debris on rail like our subject vehicle. Install new seat belt buckle and tighten fastener. Be sure to properly route wiring harness and confirm pretensioner electrical connector is properly seated. Lift seat into vehicle, then reconnect electrical connectors. Install seat and seat belt fasteners and tighten.

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Comments and Suggestions:
Justin Comments: My seatbelt light is permanently on, even when my seltbelt is fastened properly. Is this also the pretensioner?
January 31, 2015
  Followup from the Pelican Staff: Yes. Could be. Or the wire connecting to it. - Nick at Pelican Parts  
Ross Comments: My driver's side seat belt is slow to retract. Can I just lubricate it to bring it back to working condition? If so, how could I accomplish it?
January 16, 2015
  Followup from the Pelican Staff: No way to lubricate it. The reel return spring may be worn. - Nick at Pelican Parts  

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Page last updated: Fri 12/9/2016 02:20:58 AM