Two months ago I got a CEL. I used a Peake Research R5/FCX-11 to read the error codes - Table 16, Codes F5, F6 - Secondary Air System Flow too Low. I replaced the Secondary Air Pump and Valve at the Exhaust manifold. Everything has worked great until yesterday - I took the car out and drove approximately 60 miles. As I exited the freeway (thus the car was up to temp) I got a CEL. When I checked the codes - Secondary Air System Flow too Low (Cyl #4-6 only). I have verified the pump is working properly.
What else can cause this?