Airbag warning light stays on after seat swap
 

I just replaced the front seats of my 3.0i with the ones from my old 4.6is and I'm now facing an airbag warning light, caused by error codes "driver's seatbelt buckle" and "passenger seatbelt buckle". The errors also state "ground fault/resistance too low". So both seats are giving an error. I didn't touch the ignition when the seats were out and the battery was disconnected anyway. Now when clearing the codes with INPA they just come back immediately so clearly there is a persisting problem.

I have already cleaned the seat's electrical connector and the connector for pyrotechnic seat belt tensioner with pressurized air but that didn't help.

Granted that it was three years ago, but both seats were just fine in the 4.6is and it would be odd if both had the same issue now. Not impossible of course. Also I guess there shouldn't be any compatibility issues between E53 seats?

Has anyone had a similar issue or have ideas what to try out or how to diagnose?

Seat belt buckle switches are active only on US versions. Could this explain the difference?

Both are euro cars so in that regard they should be the same. Also I'm not 100 % sure about the names of the error codes, they were translated from German to English. But it seems like they are referring to seat belt buckles.

Buckles or tensioners? What did it say in German? If it's for tensioners and too low resistance the problem must be on the locking part of the tensioner connector not separating the shorting splines on the tensioner side. When the connector is removed it should change the code to too high resistance.

The original German codes:

Gurtschloss Beifahrer/Fahrer (passenger/driver seat belt lock?)
Fehler aktuell vorhanden (error currently exists)
Masseschluss/Widerstand zu klein (short circuit/resistance too low)
Fehler nich sporadisch (error not sporadic)

To my understanding "Gurtschloss" is referring to a seat belt lock/buckle and at least image search is showing lots of pictures of buckles.

Disconnect one of the tensioner connectors and see if the code changes or you still have those original codes with a third one after you have erased the codes.

Okay I have now tested disconnecting the passenger side connector for the tensioner. The same error "Gurtschloss Beifahrer (passenger seat belt lock)" with all the other same information still there still exists, but I also got a new error:

Zuendkreis ZK2/Gurtsrammer Beifahrer (Ignition circuit ZK2/Seat belt tensioner passenger)
-Fehler aktuell vorhanden (error currently exists)
-Widerstand zu gross (resistance too great)
-Fehler nicht sporadisch (error not sporadic)

The new error has the line "resistance too great" which you referred to earlier but the old error stayed unchanged with the "resistance too low". Could this mean the "Gurtschloss Beifahrer" is not directly related to the tensioner but there is some other mismatch between the seats?

Then it must be related to hall sensors on seatbelt buckles. The actual part seems to be the same on E53 after 9/2000 so that doesn't explain it. After looking on the MRS coding options it seems that Euro models after 3/2003 are coded the same as US versions regarding this buckle sensor. So there must be a wiring difference in the seat wiring between main connector and buckle (2 vs. 4 wire sensor mentioned on the coding). If you are familiar with NCS you could change the coding on MRS module.

Put the two VIN info real oem and compare the seat models to start with.

The only thought that comes to mind is the seat module: isn't there a module under the seat that splits the connection from the car to the heater/butt sensor etc? Different model/programming interfering?

https://www.realoem.com/bmw/enUS/sho...diagId=61_1220

https://www.realoem.com/bmw/enUS/sho...diagId=61_1220

Here are the two pages for the seat wiring for example for the two cars start there see if there's a different wire that may have missing pins.

I didn't find the page with the seat modules yet but you can browse the two sets and look for where there's a change in the part numbers or see if you can swap the electrical parts under the seat.


–awr–

Using Tapatalk VIP on iPhone

Seat module on E53 is only for moving parts and memory. MRS components and heating are directly wired from the seat main connector.