codes on a 05 prius

ok so I just got this car the check engine light was on I scanned it. it gave me code p1121 no big deal got the water coolant valve going to replace it.. the a/c don't work in the car so I figured out the cooling fans aren't kicking on at all and neither is the a/c compressor but the car has plenty of Freon.If you drive the car its fine but if you let it just idle after so long the red light, the yellow light, and vcs lights all come on, car runs normal but as soon as you turn car off it wont re start until you erase codes. so I did some further research and o REillys scan it they got codes p1121( which I know),code C1242(open circuit in ig2 circuit) and C1300(malfunction in engine control unit). does anyone know whats these codes mean or anywhere I can start to try to fix problem(s). The cooling fans do work as I did a by pass test to check them and I done replaced the 2 cooling fan relays. thank you for any help.