A voltage drop test;
Pos on the lead battery nub.
Neg on the wire end terminal that surrounds the battery pos nub. You should see very close to 0 volts.
Next test the connection from the wire terminal end to the twisted wire itself. Again should be close to 0 volts.
Then from one end of the twisted wire to the other end of the twisted wire down by the starter.
You starting to see the pattern? Should be close to 0 volts every time you go across a connection.
Going from battery pos to the s terminal caused the relay to close, sending current to the starter. If the key was on then the truck would fire up. Doing that isn't part of a voltage drop test.
I have to go now but will check in later. Maybe
@adsm08 or
@RonD or someone else can help.