Yeah, sorry - I'm not being very clear here, hopefully the attached photo will help.
Here's some VVT solenoids (and others) just as an example - each has two wires going to it. As you can see, they all receive voltage from the same IGN +15 rail, through 7.5 amp fuse R8, distributed to the different solenoids through E42, E43, E44 etc. But clearly, the VVT solenoids are not energized all the time; just some of the time, and the signal that allows them to energize comes from the ECU, i.e. E50/pink-red, attaches at ECU pin CB2. The solenoids are designed so that without the signal from the ECU, they are off, and they turn on (accept voltage from the rail) when the ECU signals the solenoid.
I can measure the voltage from the rail, of course - it is steady, and a known quantity. My question is, how do I know when (if) the ECU is sending a signal to the solenoid to activate? This is going to be intermittent, when the engine is running, and an unknown quantity.
OR, maybe its easier to post the actual problem. I regularly get a P0014 Bank 1 exhaust cam out of synch code when I drive over 4,000 rpm. I've replaced the sensor twice with no change. I've removed the solenoid and it's clean and jumps when voltage is applied, so the solenoid itself seems good. This means either the solenoid is not getting the signal to advance the cam, or the cam was installed incorrectly - or maybe something else I haven't thought of yet (?). So before I go through the mess of removing the valve cover, I was hoping to test the output from the ECU. Make sense?