I have an Audi A3 2.0 FSI SE 2003 (First of 'new' shape). I have had 4 fault codes come up as follows: 1) P0011 - Bank 1 Camshaft A Intake Not Reached 2) P0420 - Catalyst System Bank 1 Efficeincy

SOURCE: I have a P0420 code catalyst efficiency below

it is a bad converter not o 2 sensor i would change the cat and both o 2 sensors

SOURCE: 1997 lincoln town car 4.6 with a p0430 fault code

I will make an assumption here, we know what the root word means. This code was extracted from the computer by? What this is telling you one of 2 things: The Bank 2 oxygen sensor down stream of the catalytic converter (there are 2 converters, one for each bank of cylinders on the 4.6ltr engine) is bad and/or that the Bank 2 catalytic converter is no longer doing the job it was designed to do. Simply, Catalysts wear out. They are good for approx 100,000 miles (as required by Federal Law). Again, I assume that the reason the intake manifold was replaced was because it had a crack in one, or more, of the runners? (part that feeds the head of a manifold). It may have taken a while to find this as being the cause of why the car running incorrectly, maybe rough. This means, that during the time the car was being driven with the problem, the amount of unburned, or not within spec exhaust gases, coming off the side of the engine affected by the intake issue was higher than normal. This out of balance level of exhaust gases were being dumped into the converter on that side of the engine, thus causing the converter to have to run hotter, work harder, or even at the time the gas was being processed through, causing deposits to be formed in the converter, thus shortening it's life span. The Bank 1 side of the engine, apparently, did not have the issue and it's catalytic converter's life was not affected. I hope this makes sense to you.

SOURCE: just failed an emissions test due to a fault code

could be a bad o2 sensor, you'd just have to look at the pid data on a scan tool to know for sure. odds are good though its a bad catalytic converter. they all have an 8 year/80,000 mile warranty on them but if its out of warranty they can be quite pricey

SOURCE: received fault codes P0420 and P1296 catalyst

Not sure on the P1296 code, however in 95% of the cases the P0420 code means the catalytic converter is bad. See P0420 and P0420.com

SOURCE: i have 2 trouble codes on my 2002 dodge ram 1500

9 times out of then this points to bad cat and the cat will need be changed.

Other things that can cause this code are an exhaust leak before the front 02 sensor or the car in need a of a tuneup badly. Generally if this problem is sensor related you would have other codes also.

If you want to know of the cat is bad the computer stores data and when you have a data scanner that can access MODE 6 the data can indicate whether your cat is the issue or not. Its a bummer you have to have this diagnosed by a professioal to get this data since the scanners do not get loaned out.

I have heard of alot of cats that were replaced for no reason because of other reasons so be cautious on how to address this because your not going to be able diagnose this without a data scanner and all the specifications for the sensors.