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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:

T50 Torx, flathead screwdriver, 3mm Allen, plastic trim tool

Applicable Models:

BMW Z4 Convertible (2003-06)
BMW Z4 Coupe (2006)

Parts Required:

Seat belt buckle

Hot Tip:

Disconnect battery before disconnecting seat connectors

Performance Gain:

Remedy fault code for seat belt pretensioner

Complementary Modification:

Replace opposite side buckle

Front seat belt buckles in all BMW Z4 models are equipped with pyrotechnic automatic pretensioners. 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 55 mm (about 2 inches).

The pyrotechnic pretensioner 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 to prevent accidental reconnection.

The seat belt pretensioners can fail over time and will set a fault code in the airbag (MRS) 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 pretensioner 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.

This article will also cover replacing the seat position switch. This switch sends the seat position to the multiple restraint (MRS) module for use in airbag stage deployment.

Interior trim pieces in BMW Z4 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 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. Questions or want to add to the article? Leave a comment below. When leaving a comment, please include your vehicle information.

First you have to remove the seat that requires the new pretensioner (red arrow) and seat belt buckle (blue arrow).
Figure 1

First you have to remove the seat that requires the new pretensioner (red arrow) and seat belt buckle (blue arrow). See our tech article on Removing Seats. Place the seat on the ground or workbench.

Detach the wiring harness (red arrow) from the seat rail.
Figure 2

Detach the wiring harness (red arrow) from the seat rail. Pull the clip straight out to remove (blue arrow). If needed, squeeze the clip tips from below to fit it through the hole in the seat rail.

Then tilt it back to access the electrical connectors under the front cushion and the belt buckle.
Figure 3

Then tilt it back to access the electrical connectors under the front cushion and the belt buckle. Release the two retaining tabs by pressing them toward one another (red arrows). Hold them in while you slide the connector toward the rear of the seat. Remove the connector from the mount (blue arrow).

Next, cut the tie strap (red arrow).
Figure 4

Next, cut the tie strap (red arrow). Then, release the retaining tabs (blue arrow) at the electrical connector cover. Press the tabs away from the yellow portion of the connector and hold it. Then slide the connectors out.

Slide the seat belt buckle connector out of the main seat connector (red arrow).
Figure 5

Slide the seat belt buckle connector out of the main seat connector (red arrow).

Unclip the electrical connector (red arrow) retainer using a small flathead screwdriver.
Figure 6

Unclip the electrical connector (red arrow) retainer using a small flathead screwdriver.

Disconnect the electrical connector, then remove it from the plastic mounts (red arrow) and place it aside.
Figure 7

Disconnect the electrical connector, then remove it from the plastic mounts (red arrow) and place it aside.

Working at the corner of the seat, remove the T50 Torx seat belt buckle fastener (red arrow).
Figure 8

Working at the corner of the seat, remove the T50 Torx seat belt buckle fastener (red arrow). If reusing the belt buckle fastener, be sure to match the threadlocker color (blue arrow) when reinstalling.

Remove the seat belt buckle with pretensioner from the seat.
Figure 9

Remove the seat belt buckle with pretensioner from the seat. Remove the wiring harnesses from under the seat and guide it out. When reinstalling, be sure to get the harness in the same location as it was before. This is a good chance to clean the side of your seat. There may be stains or a bunch of debris on the rail like our subject vehicle. Install the new seat belt buckle and tighten fastener. Be sure to line up the tab (blue arrow) with the slot (red arrow) on the pretensioner. Be sure to properly route the wiring harness and confirm that the pretensioner electrical connector is properly seated. Lift the seat into the vehicle. Then reconnect the electrical connectors. Install the seat and seat belt fasteners and tighten. Reconnect the battery. Then check the vehicle for fault codes and clear if necessary.

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Page last updated: Wed 12/7/2016 03:03:10 AM