Haven't posted in a while since the check engine light has not come on in over a year. 2002 Disco II with 180k. I replaced the cats and O2 sensors maybe late 2017-ish. Truck has been running fine for the longest. Handed it off to my son who lives in the next town over. He's driven it since August last year with no engine light or any problems. Lately over the last 4-weeks he's had at least 3 times the engine light threw a P420. I was hoping maybe poor quality gas (we only use Premium), or condensation after these cold Texas fronts are now meeting warmer days. Anything else to consider? Was thinking maybe putting Stabil or Seafoam in the gas tank?

Thanks!
JB

 

P0420 means the truck needs some weed, man.

But seriously, It may just mean the downstream O2 sensor is bad. Did you replace all four in late 2017 or just the upstream sensors?

 

What kind of cats did you go with? OEM new or used or did you get universal cats welded in place of the original setup?

 

It means the purge valve needs to be replaced. Buy a new Bosch purge valve. The old one gets gummed up.

 

NO. P0420. Is a catalytic converter code. If I remember correctly sans coffee, P0440 is a code most likely related to the purge valve.

 

Thanks for the replies. I ended up getting aftermarket Cats then had a shop cut the old ones off and weld the new ones on. All 4 O2 sensors were also replaced.

 

Hopefully it turns out to be something other than what I am guessing, but...

In my years working in shops, I have found that universal converters in modern OBD2 vehicles usually results in a comeback for a P0420. The universal converter might turn off the CEL for a while, but eventually the computer determines the converter just isn't working like an OEM, and turns on the light again.

As such, I prefer to replace with OEM cats, whether they be new or used.

 

The CEL has stayed off. Happened to come on 3 times over the course of 3 weeks after more than a year. I ordered a new purge valve and other than that .we'll see. This one came from California, so definitely not putting those cats on. LOL

 

Uck...a California car to boot! Another thing I've learned over the years: put a federal emissions converter in a vehicle with CA emissions... almost a guaranteed P0420 in a few weeks.