I installed an amp and sub about two months ago in my 545i. The stereo sounds great and I have not had any problems until I got the old "passenger airbag restraint malfunction" message on the dash. The first time I took the car to the dealer they told me they could not find anything wrong with the airbag system and cleared the code. They never mentioned my stereo install but the service advisor did mention the recall on the passenger seat sensor. He said they checked the sensor and it was fine. Well two days ago it happened again so I took the car in for service this morning. The service advisor called me back to advise my stereo install was causing the problem. He said running the hot and ground wires for the amp directly to the battery is causing such a draw on the electrical system that its causing the ECU to throw a code for the airbag system. I am using a small 100 watt amp to power my 10" sub and cannot believe it is drawing so much power or causing a spike in power to make the airbag system malfunction. I know these cars are tempermental but could this be causing my problem? I see where others have tapped into the hot and ground wires off the stock amp when adding an addtional amp to their cars....should I have wired mine up the same way? I did tap into the stock amp to get a signal for the sub.

 

You should use a body ground. I'm running a Polk Momo 300.2 series amp. RMS power output is 550 watts @ 4 Ohms powering 2-12" Polk Momo subs. No issues whatsoever. Been running it for a couple months now. I tapped into the stocker as well for audio, the trunk 12v power socket for remote turn-on, and the positive terminal for fused amp power main. The short ground (about 7") was tapped to the cargo tie-down bolt. Let us know what happens - good luck man.

 

To the OP

Yes its happened to me. I ran the + and - directly from the battery, it blew my alternator and I got the same message as you, Passenger Restraint System Malfunction......., I thik the dealer is telling the truth. Because I did the same install on a buddy's car, and the same thing happened, blew alternator and same Passenger Restraint message.

 

There is a recall on this airbag warning error message...

 

This happend to my e46 about a month after i installed my L7 kicker with 800w amp and capicitor. i changed the mat sensor and the other small sensor located underneath the seat, it never went away!! Now i know for sure it was the system!

 

Try adding a capacitor to your system. This should stop the spiking of power caused by the amp. The hot wire should be fine going to the battery, but you should probably run the ground somewhere in the trunk.

 

Well my aftermarket amp and sub have been disconnected for two weeks now and the damn message popped up today.....I guess the BMW dealership will probably tell me it came on because the amp was not hooked up this time. I called the number for BMW that is listed on the net for questions regarding the recall. The guy I spoke with told me to contact the dealer and speak directly to the service manager....not the service advisors. He said I definately have a problem that is similuar to the latest recall notice that will be going out next month. Before hanging up he told me if talking the service manager at my local dealership did not work try going to another one.