No Illumination wire on factory harness

Installing aftermarket head unit and the attached harness adapter has no orange or illumination wire. Testing all the wires I get one 12v on constant...one 12v with key on to acc... but no orange illum wire on adapter for 12v headlight on power.. If I check all the pins I see less than 3v on one without a wire going out...but that's not 12v or effected by headlight switch... should I remove adapter and cut factory harness to recheck wires Or...how can I tap into headlight power and create a proper connection to the illumnation wire on HU? TIA

 

When I wired my head unit in , I had 12 volts for illumination .
What year is your truck ? WHAT YEAR IS YOUR TRUCK ?
I did a write up a couple years ago when I installed my double din head unit . It may be relevant if your truck is 2nd gen
https://www.tacomaworld.com/threads...ab-2010-with-pics-and-prices-write-up.364009/

I should have the factory FSM for your truck with all the wiring diagrams .
Send me a pm if you need the info

WHAT YEAR IS YOUR TRUCK

 

Part of my problem is I already purchased an adapter that apparently has no illum wire and I cant seem to locate a headlight switched 12v pin on factory plug so I'm thinking I may have to make a manual direct connection or perhaps to fuse box with a fuse if possible and I'll cut everything off and start fresh before I spend more $.

 

What year truck? Is your dimmer switch turned down(idk if that wire is effected by the dimmer or not)