That's why I was saying the multimeter would average (the square wave) out to be a voltage somewhere between 0 and 12V. It doesn't really matter what it is, you're just looking for a voltage that is more than zero and less than whatever voltage is feeding the injectors.

You don't need fancy test equipment, you just need a multimeter and a basic understanding of what you're seeing. If you want to know if the injectors are firing, you don't care about the waveform, only that they're firing and should give some slightly changing voltage that is less than the supply voltage. I'm just trying to make people understand why they're seeing what they see.

I can tell you exactly what you should do and what you should see, but that doesn't do anything to help understand why you should do that and why you should see that. You haven't increased your understanding at all unless you know why.