Hi Scotty , I know a Chrysler - why, oil under the bridge now , lol. Anyway I have 97k on my Chrys. 200 3.6L and had (other than regular maint.) had no issues with the car. Had variety of codes- got rid of all except PO420 - 07E8 replaced all 02 sensors. Brought it to reputable place they changed one 02 sensor (now all are new) and right CAT converter (right bank) code came back - took it back to same guy -he checked and got the same CAT -right bank- replaced that and UNfortunately same code came back ! That's where I'm at now, Thanks so much for help in the past and yeah I wish more than ever I leaned to Toyota Camry but to late now ! The car does run strong, did the plugs/ seals recently and the car pulls it's no slouch, 283 hp.
You did not state the model year of your car. It sounds like your mechanic may have been throwing parts at the problem rather than engaging in deeper diagnostics.
Here are some possible causes of P0420 and as well as suggested diagnostic procedures:
https://www.walkerexhaust.com/support/tech-tips/diagnosing-catalytic-converter-p0420-code.html
https://www.carparts.com/blog/p0420-code-catalyst-system-efficiency-below-threshold-bank-1-2-2/
https://www.obd-codes.com/p0420
Be sure that your electrical system is basically OK, battery and alternator in good condition and battery terminals not corroded. Voltage problems can cause all kinds of spurious problems in modern cars.
Brought it to reputable place they changed one 02 sensor (now all are new) and right CAT converter (right bank) code came back - took it back to same guy -he checked and got the same CAT -right bank- replaced that and UNfortunately same code came back !
The catalytic converter was replaced and there's still a P0420 code?
