tezscooby

Hi all I'm new to this so you will have to bear with me. I'm hoping someone out there can help i have a 1994 impreza wrx import i have had it for about 2 years and had no real problems until my speedo cable snapped which sent the car into limp home mode with the engine check light on. as my scooby is my only car i continued to use it while i was hunting for a new cable which took me about a month i have fitted the new cable and converter and then did an ecu reset which seemed to sort it but the next day the Engine check light came back on so i read the codes and they came back as 24 Air Control Valve or Circuit , 33 speed sensor and 42 Idle Switch or Circuit so thinking that it was the idle control valve i changed it. i then did the ecu reset again and again it lasted about a day so now I'm stuck not sure why code 33 is coming up as speedo is working and as for the other 2 codes I'm lost. if there is anyone out there that can shed some light it would be great