PCM reflash question

Hello I have a 2008 silverado 1500 4×4 5.3L. It was down for around 2 years, because of some surgery’s, with no battery connected. Now that it is running I’ve had to fix a few things. I replaced the complete evap system from clogging, I also had a gas leak so I replaced the fuel pump module.now I keep blowing a p0420 code. I’ve done a few things, but today I tested the fuel pressure & found it was 60 psi running, I know it should be 43 to 45 running.Since the battery was disconnected for 2 years should I try reflashing the PCM just to be safe.
Thank you for a y feedback.
Steve Harris

Topic

[Dave TidmanParticipant]

Since the programs in the ECU are stored in non-volatile flash memory, I don’t think a re flash would help. If there was an issue, the ECM would usually throw a code that says something like ECU error.

P0420 is a catalyst efficiency code. Given the vehicle sat for a couple of years, I would tale a look at the upstream and downstream O2 sensors and do the other P0420 diagnostics. See this ETCG link: https://www.youtube.com/watch?v=9VZ5K8n5jj0

[Richard KirshyParticipant]

Unless there is a TSB involving your specific issue due to software issue(s)that would require a ECU update.
I would not mess with a reflash.

[JamesParticipant]

“P0420 is a catalyst efficiency code. Given the vehicle sat for a couple of years, I would tale a look at the upstream and downstream O2 sensors and do the other P0420 diagnostics. See this ETCG link: https://www.youtube.com/watch?v=9VZ5K8n5jj0”

That’s a good video tutorial, Dave. We’ll just finish installing the parts from napa and 4Wheelonline and we’ll start working on buddy’s Silverado having the code.

[Author]

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