That is not the way professionals would fix this. If you can get your hands on a "noid" light, that will show if the injector is being pulsed by the computer.
Originally you said you were missing the 12 volts to one injector. All four must have 12 volts on their gray wires when the engine is running. If it's missing on only one injector, there's only a few inches of wire to inspect and one splice. It's a lot easier to fix the damage than it is to solder in another wire.
If it's the ground / control side that isn't being grounded by the computer, all four injectors have their own wires, and there's four "driver" circuits in the computer. Some engines years ago used "batch-fire" where two, three or four injectors were fired at the same time, and there were typically two batches, or groups. That reduces the number of circuits in the computer but it guarantees some of the injectors will squirt their fuel when their intake valve is not open. With sequential-fire, each injector is timed to open at the right time.
My fear, besides incorrect timing, is each driver circuit is designed to handle the very high current of one injector. If you add a second one, that will double the current and possibly take out that power transistor. Chrysler used to run fresh intake air through their Engine Computers to cool them, and they had almost no failures. GM had a real lot of failures, although not necessarily for this problem. I'd feel pretty sad if you destroyed your computer.
Gotta sign off in ten minutes. I'll be back in two days to see how you're doing.
Wednesday, February 17th, 2016 AT 6:18 PM