Hi guys,

Finally got my car on the road after two trips to Canada to get the new engine installed and subsequently repaired. It's running good but last week the SES light came on and I read the code and it's a P0420. This seems like it could be a bad sensor since the car has 160k on it. I am concerned though that it could have something to do with the new engine too... I should also mention that I've had the car back for a little over month with no code and it's just now throwing it. I also cleared the code and it came right back the next day.

Not sure what to check or even where all the sensors are. I'm sure being around the exhaust lines they're not going to be easy to get at. Just not sure what to check first.

I thought I'd check the basics first - make sure that my air filter is clean which most likely it is. I believe I replaced it at the first oil change.

Aside from that I really don't want to go throwing parts at the car to try to fix it. I would prefer to take a diagnostic approach to it and see if I can track down what is causing the issue.

Any help is of course greatly appreciated!

Rich

viewtopic.php?f=8&t=12335&p=131397&hilit=P0420#p131397

Post #10

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Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

That says to check the freeze frame data... I have it but I'm not sure what I'm looking for...additionally I'm not sure how many frames I am looking at - I stopped after reading through 5 or so.

Next it says how to cause the code to set again - I cleared the DTC one night and it was back on before I got home the next day so it came back rather quickly.

I have not been under the car to look at the cat, exhaust or the sensors... don't even know where to find them. I'm thinking I may want to get a set of ramps to put the car up on to do the looking... jacks and stands don't seem to be high enough. It would be nice if I had access to a lift.

Rich

Any futher help?
Rich