Look at rpm sensor , it is what the secm
Reads to send voltage to lock off
It is usually in front of engine by crank pulley
As engine spins the rpm sensor reads the crank revolutions and sends info to secm to power the lock off , the secm is not a cheap item

so a couple days after the last reply, big forklift place near me here in Florida charged me $440 to diagnose the vapor solenoid, I had just paid them to do a service a month earlier, before the problem happened. They they brought no parts which I specifically asked them to bring common parts, as they are 2 hours from Clearwater, and they wanted $1100 to replace the solenoid, I am not made of money, so I bought the exact oem solenoid on amazon for $250 and replaced, noting a lot of oil foam inside the cavity (I checked oil level and they had overfilled about 1/4" in the dipstick, grrrr..) I also noticed they had really boogered up the wire leads to the solenoid and the wiring connector instead of using piercing probes to troubleshoot, I could see the copper was shiny, so the work was fresh. i was frustrated.... Then Hurricane Helena put 4' of water in my house and forklift repair was put on the back burner since the neighbor has a FG15 I could borrow. 195 days later, I am in my house and I put a DMM and piercing probes on it and I get no voltage on my unit whatsoever. I walk over to my neighbors and their FG15 gets maybe 0.5v about a half a second after cranking then drops to a few tenths at idle... I am guessing this is PWM and my unit is not putting it out... I am guessing I need a new ECM/PCM now, but to verify, does someone have the ability to enlighten me on the wiring from the vapor solenoid back to the PCM?

Usually the signal comes from the secm
If you can you might check the voltage coming from secm to solenoid both positive and negative wires I do not have a diagram for that unit but it is same set up as a Nissan just for sake of eliminating the fuse check both sides of fuse holder for voltage I had one that the fuse holder was faulty

I do not get the initial voltage, does it come straight from the ecm/secm or go through some circuit with relays and fuses? If i take the fuse out to protect the ecm and give the vapor solenoid a little juice via an ammeter and the battery, I can hear the solenoid and a bit of gas flow and see a short burst of.5a or so..

I believe that is a low idle solenoid if it is round and has 4 screws
The small one is the High rpm solenoid
The voltage comes from small engine controller
Or secm the secm sends 4.6- 4.8 volts to solenoid. When key is turned on
It should engage for a second then shut off
That small amount of time fills the cavity with lp for starting after the start it opens and lets lp into mixer and the rpm sensor sends signal to secm that it is running and keeps it open
If it is dying I would check 1- lock off solenoid
2- rpm sensor 3 - vaporizer
The solenoid will show voltage only if engine rpm is reading