does anyone know how to address this code on my 2003 Discovery II

I had my cats stolen 1.5 years ago so I have new cats
new O2's, new MAF, new plugs wires
no exhaust leaks, no air leaks
clean intake

thanks for any input
Kevin

 

Did you replac with aftermarket cats? Those are known to fail pretty quickly compared to the OEM ones sadly. Another thing to check is to make sure your rear O2s are functioning properly. Those are the ones that tell the ECM if a cat has depleted outside of spec or not.

 

Not on my Rover, but my '06 Accord has thrown the P0420 few times. I've cleared it each time, and it returns only after many, many months. I'd try that first and see if it comes back, and how quickly. As you likely know, the post-cat sensors have nothing to do with engine management so you can also just ignore it unless a state emissions inspection would compel you to replace the cat again.

Just like the pre-cat sensors, one way to test whether the code indicates a real problem with the cat vs. a faulty sensor is to swap the sensors side-to-side and see if the fault follows the sensor to the other side.

It could also be your truck is just saying it needs some weed (420, get it?).

 

thanks for the advice
the new Cats are magna flow

I will play/swap around/ replace the rear O2's
they are relatively cheap and easy to swap/replace

O, yes my 20 year old rig needs some weed
(420 i get it)