This is long!
** Last Updated March 11, 2008 - Added Details on Airbag Control Module Recoding using VAG-COM **
So here's the write-up of my experience in replacing the airbag control module. My airbag control module experienced a 65535 - "Internal Control Module Memory Error". VAG-COM couldn't erase it. So it was time to get another one. Called around and prices ranged from $185 (from salvage yard) to $600 (new from dealer shop). I got mine for $260 from a fellow Audi enthusiast.
This job was relatively easy, just time consuming.
As always... the disclaimer to start. You attempt this at your own risks and accept full liability for anything that may happen.
This was done on an 2001 Audi A6 2.7 Quattro Automatic Tiptronic with Navigation.
Obtain your radio security code.
Connect VAG-COM to your vehicle. Open Airbag Controller Module. Click "Recode - 07" under Advanced Functions. Write down on a piece of paper the 5 digit number shown under "Software Coding". You'll need this to recode your new airbag control module at the end of this procedure.
Disconnect the battery.
Okay... here's a picture of the replacement module:
Remove the center rear vent by pulling from the top. Disconnect all the connecting wires.
Remove the intermediate section of the rear center vent (black thing). It pulls straight out.
Unplug the telephone cord by pressing the release clip and pull out.
Unplug the brake sensor (I think that's what it is) using a flathead to assist.
Unscrew the nut that holds the arm rest (Torque to 19 lb/ft or 26 Nm)
. Lift the arm rest and set it aside.
Lift the mat upward in the center console.
Unscrew the bolt underneath (Torque to 3.7 lb/ft or 5 Nm)
Remove the nut holding down rear of the rear center console (Torque to 7.4 lb/ft or 10 Nm)
Remove the cap for the brake trim using a flathead screwdriver.
Unscrew the torx screw. Remove parking brake trim. Unhook the parking brake carriage (black thing underneath the lever) from the parking brake lever.
Remove the navigation control using a flathead (skinnier the better to avoid breaking things) screwdriver and disconnect. You can see here where the hooks are for point of reference. There are 3 in all.
Using a flathead screwdriver, lift up the center wood trim at the front and pull out (1 then 2).
Remove the last two bolt holding down the rear console (Torque to 3.7 lb/ft or 5 Nm)
. After you do this, the rear console is ready to come out. Pull the rear part of the console upward, then pull rearward. Disconnect the cord to the side mirror adjustments (This can be hard to reach for those with big hands). Once that's disconnected, lift the console higher and pull forward and over the parking brake lever.
Remove cap on driver side panel.
Remove and disconnect radio. Then remove top trim (I was able to just pry it out using my fingers)
Remove the two bolt holding down the climate control. Remove and disconnect climate control (1 then 2) (Torque to 3.7 lb/ft or 5 Nm)
Fully engage parking hand brake. Place the gear in neutral and remove ashtray by pressing down on the two clips. It slides forward.
Remove the last four bolts holding down front center console (Torque to 3.7 lb/ft or 5 Nm)
Remove the front center console by pulling on the driver side panel (to get clearance over the driver side screw) and pulling rearward.
Remove the retaining clip on the vent and remove vent (1 then 2). Repeat on passenger side.
Remove the elbow vents (driver and passenger) by lifting on 1 then pulling on 2.
Remove the three nuts holding down the control module (Torque to 4.4 lb/ft or 6 Nm)
. There's not a lot of space so small pliers help to take out the nut once you have it completely loose. Once the nuts are taken out, the module can be lifted out, unhooked, and unplugged.
This is what your car will look like when you're done removing everything.
Plug in your new airbag control module. Then installation is in reverse order.
Reconnect the battery.
Hook the car up to VAG-COM and open the airbag controller. Click the recode button, and key in the 5 digit number that you wrote down earlier under "Software Coding" (if it is different than what you wrote down). Click "Do It!". Exit the controller. Key in your radio security code and you are done.
For those of you who bought a "used" controller (meaning one that was in a crash previously), before you exit the airbag controller (but after you recode the replacement module, you'll need to clear any fault codes that may exist in the module. Click on "Fault Codes" and click "Clear Codes". Exit and you are done. From what I understand, airbag control modules can be reset up to three times before it's rendered useless unless of course you got the fatal "65535" DTC.
Sorry I didn't keep track of the nut size, etc. Enjoy an airbag light free instrument console.