OS help

[L31Sleeper]

Does anybody know the difference between
OS 12212156 (base 5.7L 4L60E) and OS 12208322 ???

[L31Sleeper]

anybody ??

[GMPX]

12208322 was for 2001 models, trucks specifically used this.
12212156 was for 2002 models, it was used on all types, F, Y and trucks.
There is probably no major differences between the two OS's, usually GM just add in additional diagnostics for each revision.
In 2003 when they changed to the 1Mb PCM the ethanol tables were expanded.

For anything after 2001 there is no real need to update to the 'latest' OS unless the update address any specific issues you are having. Holden ran with 12225074 from late 2001 to 2004 without any issue until they went to ETC in 2005.