P0420 / Catalytic Converter Workaround
 

Have been thru three cat converters on my '05 Pac. The engine light comes on every 2 years and throws the dreaded P0420 code when the cat falls below 96% efficiency.

In my state it is allowable for a vehicle to pass emissions inspection with 1 monitor not complete. For the past three years I have used a simple I/M scanner, AutoLink #AL319, to reset the monitors and engine light. Then after about 55 miles of casually driving around town all the monitors will check in with a passing grade, leaving the Cat monitor as the sole monitor not complete. Duck into the nearest inspection station without shutting off the engine and she passes with 1 monitor not set.

All is good once again. Maybe I will bit the bullet and put another new Cat on it next year...

Another work around that can be done is using a spark plug anti fouler to fool the post cat sensor. Pull the post cat sensor, get 2 spark plug anti fouler s that fit the thread, drill one out so the tip of the sensor fits thru. Reinstall sensor using both anti fouler s and you will not see the code again. Has worked for me and many others

I agree, But I must live a charmed life in Western NY(tough emissions check) My last 2 03 & 04 3.8 T&C's my current 04 T&C , my 98 Avenger 2.5 all have had at least 110k miles(the vans close to 200K miles) and only my old 04 T&C gave P0420 codes...UNTIL I fixed (replaced) the NVLD(an EVAP part) sensor. NEVER had a CAT go bad on any of my many MOPAR rides!

Many thanks FIREM! That is like the best/easiest trick I have done this year. Bought a pack of two (2) 18mm Spark Plug anti foulers @ Oreilly for 4 bucks. Drilled one of em out w/ 1/2" bit. Unscrewed the O2 sensor that fits midways on the Cat, inserted said pair piggy backed anti foulers, drove Pac around a bit to burn off excess hydrocarbons from the drilling operation, reset the monitors and all came back cherry! P0420 code is gone..

Good to here it worked yet again. While I have not yet personally had a Mopar fail a converter it did work on a GM we had.

Hello:
Had engine light come on with code PO430. Cat. below efficiency. I am looking for spark plug anti-foulers that fit my 2005 Chrysler 300c, 5.7 hemi. Found a part number 42009 by HELP. Are these foulers universal or made to fit downstream exhaust?.
Thanls

Rather than drilling out a spark plug anti-fouler I bought an O2 spacer for $5 on ebay. I used anti-seize compound and I did not overtighten this aluminum part.

In California all monitors need to be ready or you will fail smog for model years 2000 and later. I used an ELM237 Wifi module and the free AutoDoctor app to check ready status. I had to drive 195 miles before the catalyst monitor was ready. Then I removed the spacer and passed the smog test.

Do not leave the spacer in place for smog test! Not only will you fail visual inspection, but your vehicle will be flagged to require replacement of the converter. Assuming the smog guys are doing their job.

Removing the O2 spacer is easy on the Pacifica. If the P0402 code reappears I will reinstall the spacer and leave it there until just before my next smog test.

Update: The code returned a few miles later, so I installed a new Mopar downstream O2 sensor. Five miles later AutoDoctor says that the catalyst is now ready for inspection. Maybe I only needed a new downstream sensor the whole time.

Update 2: Yes, I needed only the new downstream sensor. It's still code-free without the spacer.

Hello:
I installed two foulers about two months ago and no codes have shown up.
Here in Ontario, Canada they cancelled the emission testing. Just a tax grab any way.
Thanks for your reply. Stay safe and listen to the experts.