I have an update on the catalytic converter saga:
At 9600 miles codes P0430/P0431:
- replaced both catalytic converters.
At 14000 miles code P0431:
- ultimately determined the catalytic converter performance "sensor", which should have been replaced when both cats were replaced, needed to be replaced.
- Replaced both those sensors and both O2 sensors.
At 16500 miles codes P0430/P0431:
- Ford refused to replace both cats again without further diagnosis.
- Scoped both cats and each cylinder - no problems detected.
- Ford sent out a field service engineer who ran "pinpoint tests" and determined extra "fuel related" codes (did not tell me what they are) were underlying the P0430/P0431 codes.
They don't know exactly what is going on. They now believe it has something to do with the fuel delivery system but not the fuel itself.
They need to do further tests to figure out what the real problem is.
They did give me a brand new Ford Edge to drive around while the truck is in for service.
FWIW.