Check Engine Codes

I have a 1989 toyota 4x4 with the 22re. After a month of working on this thing i now have 1 more Check enginge code to get rid of.Error Code 51.The book says "Air conditioner switch on,neutral switch off,idol switch off during diagnosis check."1. will this make the vehicle not start.
2.It lists 6 possible causesA/C swicth circut,A/C switch ,A/c amplifier,TPS circut,TPS ECU.i dont have AC, TPS sensor ohms out correctlyand the computer is new. Any and all help is greatly appericiteippelled.(?)