Hi,

Got these error codes on
2001 Audi A6 Quattro, 6 cyl 2.8L

P0421 (Catalyst efficiency low-bank 1)
P0431 (Catalyst efficiency low-bank 2)
P1423
P0741

Need advice on the best way to deal with it one by one..

For P0421 and P0431 I would get the O2 sensors replaced and see if that solves the problem

For P1423 I would probably get the vacuum lines replaced

For P0741 Thinking of getting the solenoid replaced and change the transmission fluid while at it.

Hope I'm doing the right thing. Please suggest/advice.

Thanks!

 

For the catalyst codes, first be sure there are absolutley no leaks. Even a tiny exhaust leak can suck air (i.e. oxygen) and cause false O2 readings. In probably 90% of cases, if there's no leaks it's the cats themselves that are just plain worn out. They do have a life span. Of course, a person wants to be sure before spending that kind of money. It is very rare the O2's are the cause of catalyst efficiency faults.

Not sure what P1423 is off hand.................

The P0741 torque converter clutch-no power transfer is most likely the converter itself. I've run into this a number of times and in every case it was a converter clutch failure. I believe it's actually the seal on the converter clutch piston (intregal to the converter) that fails. As with the cats though, you should do all tests to be sure.

If it is the cats AND converter, best time to do the cats is when they're off anyways to pull the trans, trying to look on the bright side

 

I will consider those pointers while I'm at it, thanks for your advice!