Power from TV to POD

Not necessarily. There are separate wires for power, lights, brakes, and so on. The lights are easy to check.

For the brakes you should do a standard trailer brake check. What I do is just squeeze the trailer brake controller without touching the TV brakes, and barely moving. If you're on level ground the trailer brakes should be sufficient to stop both the TV and the TT.

For the power, it is probably easiest to use a DVM to check the voltage on the trailer battery/ies when you connect the 7-pin. With the TV running, you should see a step up in the battery voltage. Certainly over 13 volts; maybe a bit higher depending on the battery state of charge.

Our F-150 is tricky. It senses the presence of the trailer, and won't power the 12V connector unless/until the trailer is there and the truck is running. So I can't check the 12V with the trailer disconnected.

GlueGuy, many thanks, I get it. Like checking the alternator output for a car at the battery. That makes sense to me, again thanks.

Some brake controllers have a continuity mode that sends a small current to the brakes continuously -- obviously not enough to engage them -- and an indicator light, so I use that to make sure the brakes (and the plug in general) are connected.

To echo Stephen about enabling power, my '11 Silverado came from the factory without the brake controller and power wire connected.  The wires were installed but were tucked away under the fuse box under the hood.  There's even a lug on the fuse/relay box to connect them.  Easy to do, just had to buy the fuses, if I recall.