Sounds like you read a mistake or there is some confusion. You will find voltage on both injector terminals as long as it's still plugged in and you're back-probing the terminals through the rubber seals around the wires. You WILL find 12 volts on just one wire if you have the connector off the injector.
Assuming it's plugged in, one wire supplies the 12 volts to the injector, then the Engine Computer supplies the ground on the other wire to turn the injector on for a precise amount of time. During that very brief time you would find 0 volts on that "control" wire since it is being grounded by the computer. When the computer wants to turn the injector off, it removes the ground path. The 12 volts you see on that wire comes from the 12 volt supply wire and reads through the injector. I know that sounds complicated but the computer is just an on / off switch. The difference is unlike the light switch in your house that removes the voltage source to turn the light off, the computer's switch is in the ground side and turns the ground path off. Regardless of where that switch is in the circuit the result is the same. Current flow stops and the injector turns off.
If it helps, another way to look at it is you need 12 volts ACROSS, (or BETWEEN) the two injector terminals to turn it on. If you switch off the 12 volts you'll find 0.0 volts on both terminals. If you switch off the ground, you'll find 12.0 volts on both terminals.
What you should find is the test light will flicker on that ground wire when you crank the engine. That indicates the computer is pulsing the injector to spray fuel into the engine.
Thursday, July 25th, 2013 AT 8:06 PM