Well, you are down to only 1 code, that is progress, right?


Anyway, does the pump run? It usually runs at cold startup to provide extra oxygen to the cats so they heat up faster.
It's pretty loud and obvious. Do you hear it at start up? If not, it either isn't getting power or the motor in the pump is bad.
If it IS running, then I'd guess a sensor is lying to the system about the pump not running.