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Thread: 1998 BMW 528i, Replacing Driver Seat Belt Buckle (Pretensioner)

  1. #1
    Join Date
    May 2006
    Omaha, NE
    My Cars
    1998 528i 5-spd 102K

    1998 BMW 528i, Replacing Driver Seat Belt Buckle (Pretensioner)

    DIY: 1998 BMW 528i, Replacing Driver Seat Belt Buckle (Pretensioner)

    I have Air Bag Light on the dash for almost 2 years now. Scanned with Carsoft Version 6.50.

    Related thread here “Any Carsoft expert here? Codes 16, 24”:

    It turned out to be Driver’s Buckle (aka “Pretensioner”).
    PN 72118240045: $150 at local BMW Dealer. Don’t even try to buy this online, because of the explosive charge inside the assembly, most online vendors won’t ship it. So buy it from BMW dealer only!
    This part varies from year to year, so ask your BMW dealer for help, or you can use (enter your VIN).

    When you have the Air Bag Light, it could be many things. You need to scan the codes.
    Most people here use Carsoft Version 6.50 because it is cheap (since it is not the real version).
    1. Pass seat sensor (search forum)
    2. Crash Sensor(s), Front or Side: initially I thought this was the case and replaced it, see pic.
    3. Seat Belt Buckle. BMW designs an explosive charge into the assembly, in a crash, the explosive charge is fired and this will pull the steel cable downward, tightening the belt, limiting the driver torso from going forward too far. I am not too sure this feature makes any difference because my Volvo and Honda buckles do not have this feature (explosive charge).

    For those curious where the side crash sensors are located, they are under the front seat. Instruction for Front Seat removal is below.
    Again, this part (side impact sensors) rarely goes wrong, so I included here only for reference:


    1. Do nothing, just placed a black electrical tape over. This is what I did for 1 year because I know it is the driver’s buckle and nothing else, so worst-case scenario: during a crash, the seat belt will not be tightened further, similar to other cars I have so no big deal.

    2. Fix it! Finally I have some time (and money) and decided to fix this.
    Also special thanks to “bimmerteck” for his advices before doing this job!


    PN 72118240045: $150 at local BMW Dealer.

    - Torx Bit T30 (used with 1/4 ratchet)
    - Torx Socket T50.
    - 10-mm wrench for battery
    - Screw driver, Pliers etc.
    - Piece of 2x4 wood 8 inches long
    - Zip Ties


    - At appropriate time, you must disconnect the battery ground cable. Read on.


    1. Move Seat all the way back.

    2. Remove “Cosmetic Cover” using T30 bit. On the INNER side, it is tricky with tight clearance, so use a 1/4 ratchet. Then wiggle the plastic cover forward to remove. Now you have exposed the T50 bolts holding the driver seat frame. There are a total of four (4) T50 bolts: two (2) in Front and two (2) in Rear.

    3. Remove two (2) T50 Front bolts. Then move the seat all the way Forward.

    4. The two (2) T50 Rear bolts are under a plastic cover. Gently pry the plastic cover up and remove it (it just snaps in).

    5. Now there are two (2) ways to do this, some people remove the seat from the car completely, but I find this is more work than necessary. I did this with the seat in the car using a piece of 2x4 wood that is 8 inches tall.
    Since you will move the seat further Back, you will need to undo the “seatbelt height adjustment cable” thingy. Under the seat, there is a cable that connects to the seatbelt height adjustment. The “Fixing Pin” rotates and locks into the “Fixing Clip”. Note how it is setup for re-assembly. Simply rotate the “Fixing Pin” to unlock it. Then pull the “Fixing Pin” out. The “Fixing Clip” will come off.
    Confused? Look at the opposite seat for reference.

    6. Now Pull the seat as far back as possible (watch the wiring coming from the floor, don’t yank it!).
    Place the 2x4 wood under the rail to lift the seat up. This allows the T50 socket to go in to remove the Pretensioner.

    7. Now, STOP! Go to the trunk and disconnect the Battery Ground Cable (10-mm wrench).

    8. In order to remove the old Pretensioner, you need to:
    - Undo the Velcro
    - Cut the Zip Tie
    - Disconnect the 2 connectors (1 for explosive charge and 1 for buckle). They are very easy to disconnect.

    9. Now look at the old and new Pretensioner:
    - Old Pretensioner has “wire chafing”, this may be why I have the above SRS codes.
    - New Pretensioner has Protective Sheathing.
    - Transfer the Old Plastic Clip to New Pretensioner.
    - Connect the 2 connectors
    - Add zip tie.

    10. Now, install the New Pretensioner: there are 2 notches (Blue arrows) that must match the tabs on the seat.

    11. Re-connect:
    - “Seatbelt height adjustment cable” thingy.
    - Battery
    - Four (4) T50 bolts
    - Cosmetic covers
    - Velcro around the base of the buckle

    12. Get Carsoft Version 6.50 to turn off Air Bag Light.
    A few tricks on Carsoft 6.50:

    The bottom line for me:
    - Laptop Compaq Evo N600C from 2003 with the 9-pin RS232 port
    - XP Operating System
    - Install software as instructed: copy from disc to C:\. See attached pdf.
    - Then copy the 10 “crack” files as instructed.
    - You must launch Carsoft from C:\cm75f directory. If you launch the software from “Start\All Programs\Carsoft”, the software will crash LOL! So, for this part of launching software, do not follow the pdf file.
    - Go to C:\cm75f directory, find the Carsoft.exe file and launch the software from there. Listen to me, it took me a long time to figure this out!!!
    - Battery must be fully charged!
    - Key in Ignition Position II
    - Erase Air Bag codes.
    - Go to dash, the Air Bag should be off.

    That is it, boys and girls!!!

    Forgot to mention one thing: this is for non-sport seat.
    The sport seat may be different, you may need to remove the seat from the car to replace the Pretensioner.
    Last edited by cnn; 02-20-2012 at 12:04 PM. Reason: Automerged Doublepost

  2. #2
    Join Date
    Jan 2007
    West Michigan
    My Cars
    98 540iA (Prd 11/97)
    Nice, Cam.
    I'll tow this to DIY.

  3. #3
    Join Date
    Jan 2009
    Chicago South IL
    My Cars
    2003 530i Sport

  4. #4
    Join Date
    May 2006
    Omaha, NE
    My Cars
    1998 528i 5-spd 102K

    M52 is better!

  5. #5
    Join Date
    Nov 2009
    Campbell, CA, United States
    My Cars
    2002 BMW M5

  6. #6
    Join Date
    May 2006
    Omaha, NE
    My Cars
    1998 528i 5-spd 102K
    I forgot to post the DIY Passenger Seat Emulator.

    Bought the BMW Passenger Airbag Seat Sensor Mat Occupancy Bypass Emulator from ebay seller radzos from Vilnius, Lithuania; $10 + $5 shipping = $15 total.

    It is a very simple fix:

    1. Open Right Rear Door and look behind the Front Passenger Seat.
    - Cable that goes to SRS Computer is Blue.
    - The other connector goes to the seat sensor (Red).

    2. Unplug the factory connector (squeeze the side tabs and pull) and install this "Emulator".
    Then zip tie the factory cable so it does not hang down.

    Done in 5 minutes.
    Then use appropriate software to erase the SRS dash light.

    Last edited by cnn; 04-09-2012 at 10:53 AM.

  7. #7
    Join Date
    Nov 2009
    Campbell, CA, United States
    My Cars
    2002 BMW M5
    Nice write-up...

  8. #8
    Join Date
    May 2006
    Omaha, NE
    My Cars
    1998 528i 5-spd 102K
    UPDATE to this whole thing.

    Initially, the Carsoft SRS Code was:
    24 Linker Sattellit (Sidebag Sensor) / Druck-Fuhler, Beifahrer Airbag
    16 Gurt Schalter, Fahrer Airbag

    1. I researched and someone told me it was driver's Buckle (aka = Pretensioner).
    Installed brand-new Buckle.
    The SRS codes came back.
    This time I gambled and bypass it using the "Emulator" as mentioned above.

    2. The new "Emulator" works great!
    SRS codes never came back.

    So if you ever see the above SRS codes in Carsoft, the culprit is the pass seat sensor!

    PS: Now I have a brand-new Buckle LOL.
    Considering that my life rides on the Buckle (in the event of a frontal collision), it is not a bad thing to have a brand-new Buckle after 14 years of service!


    This is my understanding: this whole thing about pass seat occupancy sensor is to prevent injury to a child < 40 lbs in a car seat placed in the FRONT seat.

    Factory Setup:
    - Adult Passenger FRONT Seat: sensor tells SRS computer that there is an adult there, in a collision with more than 7G deceleration: pass airbag deploys.
    - No adult: if sensor does not sense anything more than 40 lbs: pass airbag will NOT deploy to prevent potential injury to a child (should there be a child less than 40 lbs there).

    My mod using "Emulator":
    - The Emulator simulates condition that there is an adult there. So in a collision, the airbag WILL deploy regardless if there is any pass in the front seat.
    - So if you install this Emulator, do not place any child seat on the front.
    Actually, if one searches the internet, even the government strongly recommends a child less than 40 lbs to be placed in the REAR seat, it is much safer there.
    It does not matter what car you drive, a child less than 40 lbs do NOT belong in the FRONT seat anyway!

    I am a safety-conscious person and I am confident using this mod.
    Last edited by cnn; 04-15-2012 at 09:16 AM. Reason: Automerged Doublepost

  9. #9
    Join Date
    Feb 2004
    Northern VA
    My Cars
    1998 528i
    Heres my story.
    About a month ago I got the dreaded air bag light.
    I ordered a bypass seat thingy on fleabay. Took a few weeks to get.
    Put it on, still had the light. Bummer.
    So I took it off and put it back the way it was.
    So I ordered up the carsoft from china, just got it today.
    Had to drag a pc up from the basement to my garage to use the rs232 port.
    It gave back the exact same error codes as above. I googled and found this post.
    So I thought damn I gotta replace the buckle.
    So I put back the bypass. Cleared the error. Started it up, no light.
    I wonder why carsoft gives back those other errors?

  10. #10
    Join Date
    Jan 2013
    My Cars
    2000 E39 523i
    Hi, I need some help here. I bought the car already with the SRS light on, thinking it would be a simple fix, maybe just a matter of plugging something back. If i go and check under my driver's seat, i can only find 2 connectors. The main seat connector/harness which has a sliding locking mechanism (the black one, no the newer yellow one), which is connectd properly to the other end and attached to the seat with a clip.

    The other cable i see is the cable with the 4 pin plug that comes down from the buckle, which in your case was scuffed as you highlighted.
    Now, that 4 pin plug is hanging around in there and I can see no obvious female connector to attach it to...where the hell is it supposed to be?

    Any help is much appreciated, thanks.


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