What your BM54 unit looks like Note, there are many different part numbers, but the units are the same. The only difference is the firmware version on them. Types of BM54 Faults - Amp Upgrade. The most common one, is the IC Amps failing and causing one or more speaker to stop functioning, or causing distortion. This can happen permanently, or after about 10 seconds to a minute of switching it on. And if you are really unlucky all 4 channels would have gone off. As long as you can still change radio channels, switch between Modes, and the amber light is still ON, next to the volume knob, then the unit is 100% repairable. The bonus of having this repair done, is that the sound will be improved. The usual power output is 15-20 watts, and the after the repair, you are running 45 watts. -Speaker faults. As these cars are getting older, I have been seeing more and more speakers failing. The best and cheapest way to test this, is to use a multimeter. Here is a diagram of the pin out for the BM54 connection. So with the multimeter set on the lowest ohm reading, you want to measure the + and - of each speaker input. The BM54 does not need to be plugged in for this, infact, its best to not have it plugged in, for a cleaner test. All speakers should read 4 ohms. Anything less, and its not 100% healthy. Usually, when it reaches 0, the speaker is dead. So the channels are as follows, Pins 1 and 5 is for Rear Right Speaker Pins 2 and 6 is for Front Right Speaker Pins 3 and 7 is for Front Left Speaker Pins 4 and 8 is for Rear Left Speaker This test does not work on cars with DSP or Harmon Kardon upgrades, as the speaker wires do not travel directly to the speakers. -Processor chip replacement. Buzzing, squealing type noise as shown in the video below. This fault usually starts at very low volumes, and eventually spreads like a virus, to the point that you hear at all volume, bass, treble settings. Again, 100% repairable. It is very rare to have both amps fail, and this fault to happen at the same time. However, if you do have both faults, I can do one of them half price. -No power. The amber light next to volume knob is OFF, and the controls on the left side stop functioning. The first thing you should do, is disconnect the BM54 unit for 30 minutes, and reconnect again. This will occasionally bring it back to life. The repair success on these are 65%. -Water damaged. Check for water damage inside, especially on X5s, where the water can sit at the bottom of the boot. Water damaged is NOT repairable. I have plenty of these water damaged units, my bm54 graveyard. Plenty of 100% working units available in stock. Additional Upgrades - RCA Preouts Channel Outs for aftermarket amps, is also available on request from a cost of £30. Will also come with 12v Remote cable for easy plug and play for your aftermarket amp and sub installation. Auxiliary input options -Bluetooth Music Streaming via mobile phone, which does not effect the Bluetooth connection you already have in your car for phone calls. This is available for £60. -Iphone/Ipod connection, which will charge your device and play music via the car. This is the 30pin connection and the cost is £50. -3.5mm Jack cable, default is usually a male connection. You can have female also, which can make a nice OEM installation somewhere in your car. The cost for either male or female is £20. Please note, all cabled AUX inputs are 4-5 meters long. -Custom jobs are also available, please end me an email or with your specifics. Address To Send Your Unit To Please follow link, and print out the form. Please fill in as much detail as possible. If you have any questions, do let me know. LINK If you you do not have access to a printer, please just write clearly on a piece of paper, and place in your parcel. Please always feel free to call me on +447958499151, if you require any advice or to ask questions about your BMW System.