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peterpete190, Auto Technician
Category: BMW
Satisfied Customers: 34830
Experience:  Over 17 years diagnosing and repairing vehicles.
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Not sure if my problem can be resolved without further

Customer Question

Not sure if my problem can be resolved without further troubleshooting. Retrofitted a Bang and Oulfsen Amp into my 2013 F10 BMW and removed the Harmon Kardon amp. Yes, major retrofit, but I have been working on cars for 36 year, so adding the B and O wiring harness into car, removing everything in trunk interior, dash, etc and then installing B and O additional wiring harness is not a job above my skill set. I did this job with another guy who has a BMW shop, but he does things with speed while I am a private owner that is more meticulous. Anyways, here is the issue, AFter putting car back together I have A: A Knee air bag warning light and the code reads Low Resistance. Read .002 resistance in the wire back to the ECU on both wires to knee airbag. No other airbags having issues. Also, EVERY 7-8 minutes, I get a Pop... Pop....Pop (Think of hooking a 9 volt battery to a speaker to test it) and this popping happening every 4-5 seconds for 30 seconds and then it stops. Then another 7-8 minutes, popping happens again. I hear the electronics relay in trunk click just before popping starts. It happens whether ignition is on or off and it happens even after car alarm is activated. AMP was coded into all the Modules BUT, I have not coded the VIN to the B and O amp yet as I need someone that knows how to perform that action. So, After install, stereo works, Center speaker comes up, system plays, But i have a Knee Airbag light and AMP popping every 7-8 minutes like clockwork. I am not sure if the two problems are related or not. Possibly I thought I might have an airbag wire pinched somewhere and system is trying to reset every 7-8 minutes on that. Or the problems not be related.
Submitted: 6 months ago.
Category: BMW
Expert:  peterpete190 replied 6 months ago.

Hi, my name is ***** ***** I will be happy to assist with this today.In some cases, I may need more info to assist better.I apologize for any delay.
I try to be here most weekdays and some weekends.If you respond and I do not respond back right away I will do so as soon as I can.My info is somewhat limited on your model here but no one else has responded and would like to see if I can help here since your question has been sitting for so long.If at any time you feel that I cannot help with this please let me know.

I would have the wiring rechecked for any issues with wiring being damaged or pinched or shorted when it was installed.I suspect the amp is not compatible or that wiring is shorted or damaged causing this issue here.If this was already checked and found o.k. let me know.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service, your 5-star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.I work on delivering the best answer and help here but in some cases, it can be difficult to do without seeing the vehicle.

Thanks, Pete

Customer: replied 6 months ago.
Hi Peter,I have personally taken the car back apart and tracked every, single, Wire back to its source and have found no issues, YET. We also swapped the amp out with a KNOWN working amp of same model and still get the 7-8 minute reoccurring popping. Also noticed that if car is in the "sleep" mode in that 8 min window and you open or close one of the doors, the popping immediately starts up again. I am almost wondering if the car is sending a "whos there" signal upon wake up and then every 7-8 minutes and since the car is still seeing a Harmon Kardon amp in car, there is a signal sent causing the issue.I plan on removing the center console this weekend to verify all wires are not pinched in there as well. I know there is an Airbag module deep in the center of the F10's and possibly a loose connection is causing the Knee Airbag ONLY error to come up. That is what is odd, it is JUST the knee airbag on the drivers side, nothing else. And then I have to figure out if the amp popping is related to air bag. Again I tracked the harness wires from airbag Knee back to teh control ECU (airbag) and the resistance showed as .002 on my Ohm Meter, same as passenger side airbag.Attaching pics of code reader. I also wanted to see if you knew what in a BMW does every 7-8 minutes. Is that a Fault Recheck subroutine in the main ECU, or is that a standard system check every 7-8 minAnd as I said, I have checked every other wire, although only 2 of them going into any existing ECU modules on the car. We did have to replace the power wire of the B and O amp with am OEM larger power wire which connects directly to the battery since it pulls more power. The original Amp wire was drawing power from the passenger side Fuse box and had a much smaller wire. That has since been removed, but popping was there even before it was removed. I can send pics of my wiring, but I can tell you, I do things to OEM specs. I am a very meticulous mechanic. Just not sure of the gentleman I worked with as we were on different parts of the car.That is why I mentioned the VIN coding of amp to car, I am wondering if the ECU is still looking for Old amp and sending a signal looking for it and that is being amplified by new OEM B and O amp.Mike
Expert:  peterpete190 replied 6 months ago.

With the codes/events set here, it does look like the coding needs to be corrected.I have not myself attempted to install an aftermarket amp and tried to recode the computers to accept it but if it were me I would see if you can locate someone that can do the coding to clear out those faults and then see if the issue is resolved from there.

If all of the wirings is o.k. the only thing I can think of is the vehicle will not accept this amp at all to work properly with other electronics or you need to obtain the correct coding for it to work properly.

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time, this can be done at any time and you can still come back here and reply if needed.Your 5-star rating is appreciated

Thanks Pete

Customer: replied 6 months ago.
Well, this is not an aftermarket amp, It is a B and O OEM amp from another F10. Really no different than adding Surround view or Night Vision to car, both of Which I have performed.You are just adding the Retrofit post factory build, telling all the ECU's that then new piece is there and then car accepts it. The only thing that has not been done is to "marry" the Bang and Oulfsen Amp to the car for a matching vin. You need a guru on that.But the question is why would that effect the Knee airbag? I am leaning towards two different issues after Retrofit Surgery.
Have you seen this Low Resistance error on a Knee airbag previously? The code that is generated in the attached pics does not show up anywhere in my web searches. And as far as I can see, the knee airbag module connects directly over to the Main Airbag ECU. Could it be the connector on the knee airbag unit? Possibly from removal and install? I know a High resistance tends to mean a Short, but not sure what a Low resistance would be. And if that Knee Light could be related to amp. I am leaning towards two different issues.
Expert:  peterpete190 replied 6 months ago.

Unfortunately, this is all of the info I have on this myself here.Others here may be able to help further on this with the information you need.I will opt out and open your question up to everyone else here to see if they can help with this.I hope you can get this resolved with ease.

Thanks Pete

Customer: replied 6 months ago.
Hello, When I removed the head unit on the car, I found that the GPS antenna and the AM/FM antenna were touching each other. So, the GPS antenna lead was at a 45 degree angle and touched the Am/FM antenna lead. They are Blue and Black conenctions on the back. Also found that the Quadlock was only 95 percent closed. So a slightly loose quadlock and Antenna leads touching one another.I have the car still in parts performing some other work while it is apart, so I will test this out in a few days. My question is: Would the GPS and FM antenna touching be able to cause the popping sound in speakers every 7-8 Minutes? Doe the GPS in the car "check in" every 8 minutes as part of a location update feature in a BMW? Does anyone know?Thanks
Customer: replied 6 months ago.
Popping sound is caused by the Main ECU seeing a low voltage condition in a BMW. The car shuts down the amp to save power. Once turned off, it causes the popping and a warning message of “no Warning tones”. YOu have to charge battery, close all doors, engage alarm, and cycle a couple times. Computer will sync and eliminate condition. FYI for anyone experienign Popping in BMW speakers or receiving a No Warning tones message. Now I need to figure out a Low Resistance from Knee air bag.