So, I keep getting these codes, P0411, P0420, P0430 on my 1995 XJS 4.0 with 58K on it.

Originally I thought the secondary air injection pump was bad since I could not hear it run, so I replaced it and bought a new check valve that turned out to be the wrong one, I cleaned out the valve and put it back on and am now waiting on the correct one. After replacing the pump, I cleared the codes and drove the car to work in the morning with now CEL, on my afternoon ride back the CEL came back on and I read the exact same codes again..

In reading on line and here the 420 and 430 codes indicate either 02 sensors or Cats.. but would something in the 411 code (Secondary air injection) cause the 420 and 430 codes to show up?

Has anyone else had this issue and what finally ended up solving it? I really don't want to have to buy cats for my Cat.. LOL.

 

Anybody have a clue?

 

kthrash - just started getting CEL and P0411/0420 on my 45K XJS. Did you ever solve this?

 

I have them too. They tend to be cracks in the exhaust manifold in the AJ16 engine. I bet you have poor mileage as well

 

I checked the Air Injection Pump - It was not operating on start-up as designed. I checked the relay and then the 25 amp fuse on the block mounted on the left fender - it was blown. I put in a new fuse and it blew again. Went ahead and removed the pump and disassembled, the pump impeller was seized. I will pick up the rebuilt ($92) unit at the parts store and install tonight and advise. Hope this gets rid of the P0420 also.