Audi Repair Questions? Ask a Mechanic for Answers ASAP
The secondary air system is activated on cold starts. The PCM expects to see a certain value from each bank's oxygen sensor that is predetermined by the 'cold start' algorithm. If those values are outside the limits, a code is triggered and stored as 'pending' until the next consecutive occurrence when the check engine light comes on. Readiness tests won't run until all codes are cleared.
It is very common for these systems to fail due to carbon build up. AIR pumps, combi valves and vacuum hoses are also known to fail quite often.
as I have inspected the hoses, and determined that the pump does run on a cold start, and that I have only one code, 1423, which indicates bank 1, would you agree that I probably have a failed combi valve on the passenger side? And that it would be worth removing the valve and attempting to clean it to get it working?