I know where the pre wired brake controller harness is in my 97 Ex but I was wondering if it was also pre wired for constant 12 volt for the interior lights and battery on my trailer

 

Yes, the 7 pin connector is wired for a constant 12v (15 amp?) connection; the pin out "should" be on the connector's cover. This is a switched connection, so it will only work with the ignition on. You should be able to test this with a multimeter.

 

mine came with a flat 4 and I changed it to a 7 way but the trailer I had did not need a constant 12 volts. The new one does but I figured if the Ex was wired already it would save me some time. The 2 wires at the rear of the truck that are in a grey connector include the brake wire form the front but the other does nothing. I figured it would be the 12 volt one I needed.... Please help!

 

The constant power should be the center pin on the connector (30 amp). I use it on my truck to power a boat winch. If it's not prewired run a wire with an inline fuse direcly from the battery to the center pin.