2013 Buick Encore check engine code P0420

[p0420 frustration]

Here is another solution I have not tried yet:

 

[cromwellrj]

Check Techinical Service Bulletin 19-NA-057 (Feb 2020) for GM computer code fix (at GM dealer only) with Check Engine Light on, resetting O2 sensors (if everything is working ok)

 

[dlvaughn63]

Is the dealer the only way to get the PCM reprogrammed??...nevermind I saw it just above..