Testing fuel injectors for equal flow with tester.

2008 Ford ranger 3.0 V6

I'm using a Allosun EM276 injector tester to see if my #4 is flowing weak causing a misfire at idle.
I'm back probing the injector driver grounds at the PCM harness connector. It is very easy to access those.
I don't want to have to pull off the upper intake manifold to get to the 4,5,6 injectors, that is why I'm at the harness near the pcm.
The problem I am having is that there seems to be a constant ground on pin 52 which is fuel injector driver cylinder 1.
When I hook up the tools clamps to the battery and then only the ground (driver) wire from the tool on to the back probed pin 52 the light that shows pulsing on the tool stays solid green and does nothing when I press the button to activated it. If I take the tool ground battery clamp off the battery but keep the (driver ground) connected to the back prob the tool display stays tuned on. So basically the tool has power and ground even though the main ground clamp is disconnected. I very confused because the pcm is supposed to only ground the injector when it wants it to fire.
I have a ecu safe test light but have not tested pin 52 to see if it pulses. I'm pretty confident I'm on the right wire. I really do not want to take the intake manifold off and connect the tool directly to the injectors. Any help would be much appreciated.

You should really isolate the injectors from the circuit before using the injector timer tool. I haven't seen a 3.0 Ranger in a little while, but there may be a connector where the injector harness meets the main harness. With a diagram you disconnect the plug, ID each injector circuit and front probe the connector with the All Sun to activate them that way.

If you have an injector that's truly grounded on the control side all the time the fuel rail will not hold pressure with the key on. You'll see the pressure gauge just drop off immediately

I figured I'd take a walk through the junk yard to see if I have one before I get going on this Quest transmission job this morning.

I would disconnect that big plug and do my checks from there:

Okay I'll check for a connector like that in my truck. I can tell it is a different year because my engine has a composite intake manifold.