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.

 

If the air outputs on the diverter valve are rubber hose, you could disconnect those to feel air flow out of the diverter. You could see if it switches when you apply or vent vacuum to the control port, while the engine is running to provide air pressure from the air pump. The anti-backfire valves further down the air lines should stop exhaust from backing up while the hoses are open.

 

i have the same code poping up. i also have a 96, but with a 302. i googled p0411 to see what would come up and it looks like all the vw bugs have problems with their vacuum lines, so i check mine and the egr is under vacuumed. i traced it back to the source on my truck its on the intal mani. drivers side. i look at that line and when i went to pull it off it fell apart. check ur lines these trucks are getting old. good luck and tell me if u hear anything else about the p0411 code.

thanks,
Steven Baty