P0420 repeating 2008 suburban 1500, 5.3L, 110,000 miles

mlaniermlanier Member Posts: 23
edited June 2017 in Chevrolet
I have a 2008 suburban 1500, 5.3L, 110,000 miles.
Last year I replaced the cats, had a couple of sensors replaced, like brake/cruise control, and one lower O2 sensor.
A few weeks ago I had my local mechanic replace the rest of the O2 sensors, and inspect my car.
Well the EVAP system took a while to reset after the codes were reset, but finally did after 4 days of driving, and trying different things, like replaced the gas cap, and driving in different conditions.
Two days after getting things to come together it throws a service light, had local mechanic check it for me, P0420.
He reset it for us to see if it comes back in a few days, and we are going from there.
I am having a hard time believing the cats have gone bad already.
I have had some good people on here give me great advice for another issue on a another vehicle, so I am hoping for the same with this issue.
Thanks in advance for any help, advice, and direction on this issue,
Mike

Comments

  • mlaniermlanier Member Posts: 23
    Ok! Another question, Does anyone out there think, updating the PCM would help solve my problem? I have read that if using an aftermarket cat system this may need to be done.
    Thanks for any reply,
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