Hello all,

I'm having an issue with my airbag light on my mini cooper s. I'm getting fault codes:

90 MRSZ5 airbag control unit faulty (alive counter, K bus message 70H)
91 K bus: communication between MRS4/MRS5 and instrument cluster faulty.

I replaced the airbag control module with one from the scrap yard but am still getting the same error.

I checked power to the module, and am getting apprx 12 volts, as well as checking continuity on the K-bus line from the airbag module to the instrument cluster with no apparent issue there.

I've tried to research as best as I can and only found 1 other post regarding the 91 error involving an icelink controller that they had plugged into the stereo which was causing voltage drop on the K bus wire, but when I check voltage, I'm getting 12 volts (just for clarification I don't have an icelink, but there is an aftermarket stereo that I wanted to rule out).

Not sure where to go from here. I don't have any real history on the vehicle as I just recently purchased it. There is one other error which is error code 50 "vehicle identification in ZKE and instrumentation is different", but from what I've found online shouldn't cause an issue with the airbag module. I'm thinking there could be an issue with the instrument cluster, but I don't have any other symptoms, and unless the used airbag module has the exact same fault I'm thinking its possibly a wiring issue, but I don't know what else to test. Another thought is one of the sensors plugged into the module is causing some kind of interference with the modules ability to communicate with the instrument panel, but I don't know if that is possible

Thank you for taking the time to read, and any input would be greatly appreciated.

 

I know this is really old but I have the same issue showing up and wondering if you found the problem?

 

I did, turns out the previous owner hand replaced the speedometer. I had to use the BMW software to change the airbag module from mrs5 to mrs4. Once the speedometer was programmed to look for the correct Mrs module it worked perfectly.