these are the codes descriptions i found on line.

http://engine-codes.com/p2431_chevrolet.html these 2 are secondary air pump related, means you have ca emissions. somethings wrong with that dumb set up. being your in OH im sure you could find some one to tune that code out, and delet the system, its not needed.

http://engine-codes.com/p2430_pontiac.html

http://www.obd-codes.com/p0128 this one says your coolant its to cold, so you need to change the t stat most likely as its stuck open i bet.