Still cannot get one injector to fire.

[lennyg]

I replaced the ECM,and both Injectors. Traced wire from injector all the way back to ECM. While looking at schematic i noticed that power goes through the oil pressure switch.
Keep in mind the truck will start but ONLY runs on ONE injector. The outer cover of the oil pressure comes on and off easily. Does any one know if a bad Oil Pressure switch could cause only one injector to fire??
PLease help. My son and i bought this for his first car and We are stuck at this one issue.
Thanks:

BTW
Its a 95 5.7TBI Tahoe 2dr 4x4 automatic.

 

[lesterl]

One side of injectors will go straight back to ECM (Dark Green/Dark Blue pin A9/A16), other side should be a battery+ feed from the ignition switch which is also fed to ECM Pin E15,F15, Fuse box ECM 1 20A fuse feed all Pink wires. Oil pressure switch should have Tan/Orange/Grey wires and will only operate the fuel pump and dash guage.