BMW Repair: Airbag control module, wet vacuum, proper diagnosis

Question
Hello Tino,
Thank you again for you instruction regarding an Ambient Temperature sensor. I also have another issue. I have an airbag light on, codes in system: "03-supply voltage 01-control unit internal fault". It started after I cleaned up a car with wet vacuum in special service shop 3 months ago. Based on the code Could it be some wiring problem or Airbag control unit does not work? Could you advice. If you think this is a control unit problem could you instruct me how can I remove it? If it's wiring how can I test it?
Thank you for your time,
Vlad

Answer
Hi Vlad,
First let me provide you an insight into this matter:
  a) this is a safety issue, which pertains to the safety of the driver and the passengers of this car;
  b) the scanner you are using on this car is incapable of
properly diagnosing a beemer due to its software, it also does not have the data that will support proper diagnosis, and granted that by sheer luck it diagnoses a problem needing parts replacement, it does not have the capability to code or program any bmw control module;
  c) I do not want to be sued at some point in time due to participation in a substandard repair of a safety issue.
But I could still give you some pointers about the matter
which you could use at your own risk---
1) the codes you mentioned are not bmw codes, and they fail to mention what portion of the Safety Restraint System has supply voltage problems (SRS control module? seat mat sensor
control modules?). Ditto with the control unit internal fault.
2) and this items are not cheap items (aside from being safety related); they can also be dangerous to work on since airbag systems are known to fire for the simplest mistake
of an untrained mechanic.
3) also, working on this system needs repeated clearing of faults and coding (you can  not just buy any part and install it yourself or use another car's control module); the simple matter of removing a module, firing circuit or airbag will set a fault.
Due to the above, I recommend that you bring it your nearest
bmw dealer for diagnosis and repair. Swallow the bitter pill
for I am sure that your life is worth more than the price that you will pay for repairs.
Sincerely yours,
Tino