hey i have a 2000 a6 4.2 v8. I just got this car. have four codes poop up they are 1136 1138. and 1411 1421 i think but the 14s go to geather. I looked cant find anything. when i got the car those codes were up found out why the intake part that goes on the back off the motor was off put back on cleared codes took three days came back on?

 

P1136 & P1138 check for vacuum leaks.
P1411 & P1421 check the secondary air injection system.

 

ya the code is 1411 and 1423. not 1421. it say 1411 is bank 2 air restricted flow and 1423 is bank 1 air flow too low.. So maybe ox sencers?