: P0420 and my engine light came on.

02-08-13, 08:37 AM
My check engine light came on for the first time since owning this car. Pulled the codes and got P0420. Car seems to run fine. Erased the code and drove the car to see if it would return. After about a week of driving the car the code has returned. Everything I can find on the internet suggests that I need to replace the catalytic converter. Before I do this I thought I would ask for confirmation from the community. Any experience with this code? Thanks.

02-08-13, 01:53 PM
90% of the time it is the cat but if you have under 85,000 mile it still under warranty. Go to any gm dealer and they should do it. If not there some after market that may work do not buy walker it is a waist of money it go bad after 5 month. There is one made by bolsa that is made for 03 05 deville is a direct fit . you know how gm is the only different is the pipe after the resonator. It work great.

02-09-13, 04:07 PM
I had that code and it turned out to just need a software upgrade. It has been over a year and the code has not returned. Have the dealer check to see if you have the most current software installed.

02-09-13, 08:46 PM
Read post 4


Cadillac Cust Svc
02-10-13, 04:59 PM
If you have any questions about warranty, phigment, don't hesitate to contact us with the last 8 digits of your VIN and mileage. We'll get you information on what warranties are still in effect on your vehicle.

Sarah (Assisting Katie), Cadillac Customer Service

02-10-13, 06:55 PM
Thanks for the info guys. I'm over 125k miles so no warranty for me.