Volkswagen: Check Engine light, lambda probes, jetta 2

Question
I have a 2003 Jetta 2.0L with 34K miles.  The check engine light can on the other day and the code reader gave a trouble code of P0411 secondary air injection system incorrect flow detected.  I have a Chiltons manual for a 2002 Jetta and as far as I can determine the secondary air injection vacuum valve has been deleted for 2003.  The fuses are all good, so is there a way I can test the check valve or the air pump to determine what is giving me the fault code, or is there another cause that I have overlooked?  I also checked the air filter to be sure it was not clogged.  

Answer
check the plastic pipes for the secondary air injection system, make sure they are fitted securely and not split. also the air mass meter has been known to cause this fault, as has the lambda probes. so it is realy a specialist job to sort (and may be expensive due to cost of parts)