Toyota Repair: 97 Corolla electrical problem w/injectors, black orange, 4afe

Question
1997 Corolla 4aFe motor. Only cylinders 2 & 3 injectors are working. Manual says that the injectors are controlled directly by engine control module. Replaced module and no change. Manual indicates that a Black and a Black/Red wires control the injectors and that the ground is black/Orange. Are all connected to same ground? The injectors have two wires each for a reason. Why are there only two wires controling the four injectors? Any suggestions?

Answer
All the black/orange wires are the supply voltage to the injector windings, this voltage is constant, should be close to battery voltage but should all be the same, if this voltage is not there on the injectors that are not working then the open circuit needs to be found, the problem is not on the ground side or the computer. In case there is equal supply voltage to all the injectors it gets a little more complicated, the injectors are fired by the computer in pairs at the same time, 1+3 and 2+4 are paired together and each pair uses the same ground path through the computer which is responsible for the injector duration by turning them on and off.The grounds for the injectors 2+4 are black/red, the ground wires for injectors 1+3 are black. The two injectors that are not working are not paired and are on different connections to the computer. Injector operation can be verified by using a small test light made especially for injector connectors to test the voltage pulses, they are available at most autoparts stores, plug the light into each connector and crank the engine, the light should flash on and off for each injector, if it does then the computer is doing it's job and there is either a problem with the injectors or the engine has another mechanical problem.