Look for short to ground on the trigger wire for that injector. Typically all the injectors share a common power feed (+). The injectors are turned-on (activated) by supplying a ground to the individual injector. Each injector has it's own driver in the control module (typically). This is the case for your set-up. Simply unplug the the offending injector and back-probe each wire in the terminal. You can front probe if you're careful to not damage the female terminal in the connector. It's really easy to permanently spread the terminal with a probe from the DVOM lead so it's best to back probe the connector. You can use a small t-pin to slip past the weather seal.

First measure for voltage at each wire at the injector connector KOEO using battery ground terminal for DVOM common. One should read source (battery) voltage, the other should read zero, or may fluctuate in mV. Probe the terminal that reads source voltage. Next, move the DVOM common lead from the battery negative to the other terminal in the injector plug. If you read anything other than zero or a floating mV then the trigger wire/terminal/driver in shorted to ground. Unplug the harness from the PCM/controller to help isolate the location of the fault and use the resistance function on the DVOM. With the harness unplugged from from the controller both leads should read OL (over limit or out of limit) when measured to battery negative. Turn the key off before you unplug the harness. You may also want to wiggle the harness to see if the problem is intermittently grounding and to help locate the location of the short.

If you don't have a dvom you can use a 12v test light or a small 12v bulb in a bulb-socket with a couple of leads. If the bulb lights-up when connected to the injector terminals then you've got a shorted trigger wire.

Chances are the wire is pinched or has melted somewhere in the harness.