So I finally got rid of most of my codes but I still have the 16806 p0422 and 17087, P0703 left. I've changed the brake switch and cleared the codes but the P0703 came back, I took out one of my brake light bulbs because it had melted the light, could this be the reason? The car has a very strong exhaust odor so I am figuring that my catalytic converter went out. I've seen online that this code is for the main cat converter, just to make sure this is the driver's side right? I'm getting ready to order an after market converter and try it out. OEM Audi parts are a quarter the value of the vehicle!

 

P0422 is bank #1 catalytic converter (passengers..right)...the code can also be triggered by 02 sensors on that side. The first sensor reads exhaust exiting engine and sets fuel mixture...the 2nd sensor double checks that and the cat doing it's job. So if the reading from the 2 sensors don't "jibe", it assumes the cat is not doing it's job...which it may not be(?)

With the P0703, you may be correct...everything in that circuit needs to be right to get a dependable code reading (or lack of code).