I have a 2011 f-150 FX4 ecoboost. I bought it used with 81,000 miles. The engine light came on shortly after buying it and had the P0430 code as well as an O2 sensor code. I had the drivers side CAT replaced and O2 replaced. Approx 2,000 miles later the light came back on P0430 code. I took to FORD to diagnose, they said it was the passenger side CAT even though the code says drivers side. I had the passenger side CAT replaced and O2 sensor. The light came back on same day! Same code, P0430!!!! Any ideas? Also, I changed the spark plugs after I bought the truck since it still had the original plugs. I broke one of the boots and had to use some wd40 to loosen it. Would this have done something or perhaps the spark plugs were not spaced correctly or tightened? Could this affect something?

 

What brand 02 sensor?
What brand catalyst?

P0420 is B1 (passenger)
P0430 is B2 (drivers)

You can also have an exhaust leak between 02S1 and 02S2 that is causing funky readings on the downstream sensor.

 

i am not sure of the brand, I could look that up. I do know he only replaced one O2 sensor on each of the new CATs, could that be the issue that he didnt replace all 4 O2's? I was thinking the next step is replacing the last two...

 

Front 02 sensors monitor fuel trim of engine
Rear 02 sensors monitor cat efficiency

 

Notice power loss or gain? You could have bad afr sensors. Also there is a warranty on all smog related equipment.