I went through Echeck & failed the following codes came up on 2004 Cadillac Seville SLS

po171-po174-po300-po410-po741 & check engine light does not work.I bought another PCM.

Asked by for the 2004 Cadillac Seville SLS
you have lean codes of 171 and 174 both banks misfire codes po300,emisssion issues with air injection po410 and trans codes po741
How do trouble shoot the problems
this may be beyond your capabilities,sorry not trying to be harsh. i rec you seek the help of your mech to diag every issue.alot of people get some info and just start replacing parts that are not needed,so to prevent wasting $ get proper diag