I have a 2000 A6 2.7T with 117,000 miles. My only noticeable symptom right now is thatthe CEL is on. I cleared the codes twice, just to see what comes up and I consistently get the following:

P1606 (rough road spec engine torque ABS-ECU)
P1423 (sec. air inj. system bank 1 flow too low)
P1411 (sec. air inj system bank 2 flow too low)
P1131 (bank 2 sensor 1 internal resistance too high)
P1113 (bank 1 sensor 1 internal resistance too high)
P0421 (primary cat. bank 1 not effective)
P1624 (mil request signal active)
P0741 (torque converter clutch circ. performance or stuck off)

Just last month I replaced the ABS module with a rebuilt one. My only other symptom is that periodically when I come to a complete stop the car will lurch forward as it shifts down to first gear.

The ABS and torque converter are probably separate issues, but maybe the rest are related to one problem and are causing the domino effect with the others. Does anyone have a strong opinion as to what's going on with my car? I'm thinking I'll start with the O2 sensors and take it from there, but I'd like your input.

Thanks.

 

Probably a vacuum leak in the supply for the combi valves. Could also be a diverter valve not holding vacuum.
O2's
There might be a reflash available to eliminate this code. Otherwise youll need a cat.
Those are gonna be a torque converter. Could also be the cause of the lurch on stopping but i dont think so.
This code is set when wheel speed sensors dont all make sence acording to vehicle speed. For example, driving the vehicle on a lift, driving in situtions with lots of wheel slip such as snow,could also be a dirty toner ring causing erroneous wheel speed readings. Do you get abs aplication at low speeds?

 

Thanks, DH. This is helpful information. The reflash is not available for my car. I'm hoping that the P0421 might just be a result of some of the other problems.

My main question: Do you think I'm dreaming or could it be the case that the catalytic converterisn't actually bad?

As far as the torque converter, yes, I've been driving on some snow and ice lately. I haven't noticed the ABS engaging at slow speeds, but that doesn't mean it's not happening.

 

The o2 fault could be causing bank 1 to run too rich which could cause the rear o2 to see as a cat problem when there is really an air fuel issue. I would definatly start with the 02 before replacing the cat.

 

That's what I was hoping you'd say.