P0411 Secondary air injection system incorrect flow detected

[ib1703]

Hi, My son has anAudi A3 1.8T 2002 with the above fault. I can clear it (code reader gadget) and a few days later it's back again. Can't see anything untoward. Doesn't seem to be a trend/way to get the code back....just random. What's worst case if left?

[Alan02]

It could be a hose adrift from the motor or a fault on the motor (air injection) or wiring?

[Crasher]

The usual cause is failure of the thin ally tubular rivets that hold the case halves together, the common fix is to replace these with M4 nuts, bolts and washers.