Suggest getting a real shop manual and look at the wiring diagrams.

Your computer does not supply 12 volts to the injectors, it "sinks" them to ground. Has anything been touched before it started, like the computer disconnected/reconnected, something added/removed under the dash, some other seemingly unrelated problem happening, etc.

If the computer had been disconnected, look at the plug to see if one of the receptacles had been pushed out of the shell or if a wire seems broken. It is hard to tell with the backshell on the connector. For any computer, look at the pins and see if one is bent.....unless you have had the connector off, pins dont bend. If a pin is bent more than about a pin diameter, the odds of straightening it reliabliy are slim.

Again, a factory manual should help guide you.

mike