Hello My name isXXXXX will be glad to assist you today in answering your questions.
The air bag could be the seat belt buckle should be around 200-300 dollars and labor tor fix it should be about the same, you have to remove the seat and then the buckle.
The problem could be with the side curtain airbags which are a pain they are built in the seat labor should be somewhere around 600-700 and the part should be around 300, it could be the entire passenger air bag itself and that is really expensive over $800
For the parking brake issue I have had to replace the module in vehicles like yours and that's not really cheap around $500 for parts, and $300 in labor. Now if the module is fine and its a switch the repair is a lot cheaper. Both issues you have, have a wide range in repair cost. Depending on the diagnosis
Now with all that said you could spend $300 on the diagnosis by itself, I figure 1hour on the air bag and at worst 2 hours on the parking brake.
If you have any additional questions please let me know
Please don't rate my answer until I have answered all of your questions.
Best regards,Bryan Tillett
From experience I would think the belt buckle but have had to replace all the parts over the years.
The parking brake modules I know are junk, replaced several of these ( I had one that died on me while I was doing a brake job, would never turn back on after I turned it off)
Yeah these systems don't even communicate with each other, so its not like one fault caused the other.
For diagnosis, I recommend that all Audi owners by themselves vagcom, this software with a laptop allows you to scan and clear codes replace almost all modules (minus the instrument cluster, immobilizer, engine control module) and it also allows you to add or remove features. I have done a bunch where the cars did not come with HID headlights people have bought aftermarkets and installed them but they get a bulb out indicator on the dash, recode the module for HID headlights and indicator goes away.
For the price of a few dealership visit for a diagnostic you can do most of the work yourself, and visit the repair shop when needed. There is plenty of manuals and forums on line that will guide you through most diagnostics. And if you can use a computer you can use this tool. I think vagcom cable and software is $699 for intro kit, but they have several.
Here is the link http://store.ross-tech.com/shop/cat/VCDS.html
Figure the diagnosis for this issue alone is going to run you over $200.00
With this software you can scan both modules get the actual fault code and with a quick google search usually find what needs to be replaced
Or just clear the codes and see if they come back
I can not tell you how many cars I saw that had codes for ;seat belt pretensioners ( code will say resistance issue) all this means is someone moved the seat
Now if the code will not clear then the buckle is bad.
I have seen dealers tell people to replace modules, and the only code in the module was a voltage code, this usually means the battery went dead now this software works like the dealers scan tool so sometimes you will get codes that are only audi/vw codes they will be 5 digits (this will be the case with your air bag)
These codes are a little harder to research, but most times with air bag it will say
Side air bag igniter (all igniters are in the air bags themselves)
or it will say pretensioner (in the seat belt)
You have to know where the part is but the software will tell you a code and what the fault is.
Now sometimes faults can be caused by one part and codes will be stored for 3 parts. This is where sites like justanswer, and the forums come in handy
For instance you could get a mass air flow sensor code
and a code for a catalytic converter. Dealer would tell you to replace both at a cost of $2400-$2600 or you could replace the mass air flow sensor and clear the codes
and drive the car if the light resets for the catalytic converter then you can with this software run a test on the converters.
This software has what they call measuring blocks (to read values) or basic settings (performs adaptations, or test)
One thing every audi/vw needs is the throttle body reset every now and then with this software you can do this procedure, this ensures good fuel mileage as well as correct function.
All around there is a learning curve to the software but with all the resources on the internet you can do just about everything you will ever need to.
Now what it cant do it cant code keys to the vehicle, you cant replace the engine control module or anti theft module. This is the only down side, now to the home user this is not a deal breaker, but most automotive shops need those functions.
I have used this tool daily for the last 5 years I can answer any other questions you have about this software or any other questions you have
Bentley publishers. http://www.bentleypublishers.com/findMyCar.do?action=getresults&forward=index&make=Audi&model=a5&year=2008
here is the link to the site,