I have a 1996 F150 with the 4.9 Liter engine. The smog pump was getting noisy, so I replaced it with a new one. About 75 miles after replacing the smog pump, I recieved a check engine light. I read the code and it came up P0411 which is "Secondary air injection - incorrect flow". I figured that the new smog pump was the problem. So I took the pump back and exchanged it for another one. Shortly thereafter the code returned.
I have checked all connections to the smog pump and everything in the vicinity. I cleaned the smog pump air intake filter as well. I consulted my local Ford dealer and they suggested I put a vacuum on the diverter valve and see if it is functioning. I have done this and while I do hear movement internally, I have no way of being certain if it is operating 100%.

I can clear the code and it generally will not come back on during stop-and-go driving, but highway driving will bring it back. The code everytime has been P0411. I now have over 500 miles on the smog pump, so I know it is not a break-in issue.

Any suggestions would be appreciated.
Thanks.

 

Check all the vacuum lines first . Sorry , I dont have any diagnostic routines to help you out .