2003 spectra automatic transmission problems

I just purcanhased car and now the tranny wont shift into third or forth gear. After driving for a long while it will shift fine sometimes. The od switch in shifter only works after car goes through all gears. The dash light only comes on then. No check engine light is on but had the date stream ran for codes. 1) po604 short in wire harness between tcm & output device. 2)po760 shift solanoid c failure or short in whire harness between solanoid & TCM code 3 shift solonoid a or b failure low line pressure foss faulty speed sensor. No one knows if this even means anything. The tranny shifts fine once it goes through the gears and the fluid is clean. If you could give me any advice (other than I shouldnt have bought it) Please let me know