Driving to work today I got a P0420 on the navi display. From checking around online it looks like its the rear bank warm up catalytic converter. Has anyone else had this happen yet on a 2g RL? I think im gonna replace the post cat o2 sensor before I change out the cat just because its a only $100 versus spending $500 on the new cat. If I change out the cat I will change out both sensors anyway. What do you guys think?

 

I would strongly recommend changing out the post-cat o2 sensor as this is a likely culprit for the code you've specified.

You'll also want a way to reset your CEL codes; this can be done for free at Autozone/Schucks/etc or you can purchase a OBDII code reader that can do it for ~$100.

 

Thanks! I hope that’s the case. OEM cat converters are so expensive lol. I've got an OBD2 scanner so I can clear the code with that. I’m getting ready to leave for a 2500 mile trip on Friday and fixed or not I’m taking the RL. Since the code only relates to the bank 1 cat and post cat o2 sensor I’m still ok driving it. A new post cat sensor is supposed to deliver tomorrow so hopefully that will take care of it before I leave.

 

I'm pretty certain that it will. Switch the sensor out, reset your codes, and start her up. I'm betting she'll run good as new. Good luck

 

I changed the sensor a couple hours ago and so far so good. I’ve put about 30 miles on it since, and the CEL is still off. Ill let you guys know in a few days if it stays off.

It was a pain to get the stock sensor wire unclipped from all the little brackets behind the engine since I couldn't see anything. It had to all be done by feel. The only part the had to come off to remove the sensor is the J-pipe so it only took me ~45 minutes

 

Well Im about half way to my destination with 500 miles since putting the new sensor on and all seems well. I checked the car with my scanner and it says all the emissions tests that the ecu runs are complete including "catalyst monitor" so ill let you know if the light comes back at some point in the future.

 

1150 miles and the light is still off. I'm confident that the issue is fixed.

 

I had the same code pop up on my 2005 RL with 98K. I replaced the same rear bank sensor as you and the light was out for about 400 miles and then came back on, then went out. Before it was on all the time and now it is intermittent. It will only stay on for like a day and then go out for a week or so and then come back on. Any ideas????