Slight recap first. Car had P1647 Code when I bought it. It also had dry rotted Tires. First Time I really got to drive the Car after I changed Tires Heater Hose blew (Pulling out of my Driveway). Had it towed to the shop for repair. After Hose was repaired got a call from the Shop saying Car was running badly and Restricted Performance Light was on. Picked up Car and drove it Home (about 3 Miles) with the Restricted Performance Light on. Changed all the Plugs, Coils and O2 Sensor for P1647 Code.


Car ran great. No misses nor P1647 Code. After about 100 Miles P0420 Code came up. I cleared it and it came back on in about 40 Miles. Car is running great. How worried should I be about the P0420 Code? Will it hurt anything if I continue to drive the Car with this Code? Could something other than the Cat Converter be causing the Code?

 

It may be the connection to the oxygen sensor or the sensor itself. A diagnostic reader will allow you to monitor the sensor while running and compare to the other side.

 

RJ237 is kinda right, but from what the car went threw, I know its a cat. See O2 codes are usually thrown from the before cat sensor, they measure fuel mixture, and tell the ECM/ECU. They do some work. The bad cat code is thrown by the after cat o2 sensor, and he doesn't do ANYTHING but see if cat is working. If he sees same amount of stuff coming out that was measured by front cat going in, he throws that cat code. and thats his only job. Most bad O2 are the front ones, as they heat up and burn out.

Now the kinda good, and really bad news. Most of the time, its one bank that had issues. Bad plugs may kill a coil and that may take out that bank's cat. The other cat should be fine, they both don't need replacing if one goes down. When treated right, they last life of car.
But because the precious metals in them, they are EXPENSIVE for OEM, which you should get. Aftermarket coils and cats for Jags are pure crap.
But, again back to cats lasting as long as car, you could find a Jag part out place, and buy a cat from a junked. Its illegal to replace cats with used, but don't make an issue of it, right? It will save you thousands. Plus every Jag owner needs a "guy".
Now as for running car with a bad cat, no worries, you can. All they do is clean the exhaust. You may have some performance hesitation as exhaust on that side maybe blocked some. And of course the annoying CEL and cannot pass smog.
Now I kinda think driving a Jag around with a CEL, is like having an iPhone with a cracked screen. While common, it's just so ghetto. (kidding, no offense)

 

It will get changed. Just didn't see any of the symptoms described in other threads. No Rattles, no loss of power etc. I just have to decide if I can do it myself or bring it back to the shop.