recently i had fixed pcm rebuilt and put in new fuel pump and got truck running again. Well i turned on the headlights and they did not work but the parking lights did. After watching utube video i took 30 minutes to take dash out EASILY not rough. and removed 3 screws to the power mirror adjust to gain access to light switch. Ran ohm test on switch to see how it worked. Here how. Parking lights first since they worked. B2 is hot wire and is red . pull out **** to 1st notch and it energizes R which is yellow black wire. The yellow black wire goes to all 4 corners of truck to light up each lamp, also at this time I becomes energized and the instrument panel lights up which is controlled by the spring coil at front of light switch. I is tan or biege color which run instrument cluster. Also if you look at the LF parking light bulb you will see the yellow black wires for parking lamp and 2 green wires for blinker filament. most likely one for turn signal one for hazard flasher. now the dome light is yellow wire and goes to D. When you click on dome light it grounds D to light dome.
Headlights 12v hot on blue wire which is b3 ,pull **** out 2 notch and b3 makes contact withe U which is black blue wire. Now here is the conundrum , i placed a jumper wire from B3 and U and pull **** to 2nd notch and lights came on. Yeah . Now the hi beam circuit works fine.. Why? If a cuircuit breaker is inside switch why would bypassing this make it work like normal. But P is always hot and is green black and energizes H which is green. This truck runs lights thru multi function turn signal.. I also used hayes 12-31 page at the back of book and 12-7.

 

Here is a print i have, Check you have power at B1. With the headlights on you should have power at P and H. If not the circuit breaker is bad.

 

of course, didn't get it quite right. One of the blue b3 is jumpered and runs to rear for power via the harness by the steering wheel for maybe LP light and such. The other blue b3 which has the power i couldn't find its origin but i did not think to check the key. One of the U black, blue goes to pin 4 of the pcm it would seem i couldn't find where the other U black, blue wire goes, will check key for that too. 12-7 in hayes book states that low is 18 and 19 and hi beam is 19 and 20 of the multi-function switch, but mine is 23 which is green most likely coming from H on switch and then it is transferred to 22 for the high beam which is red orange and runs to lamp. Then 23 again with the multi-function switch in normal position transfers to 24 the purple, white wire and runs to the lamp for low beams, which i have no continuity in this circuit. It is open. So new multi-function switch it is so low beam will work. recap continuity from23 to 22 and not in 23 to 24.I will have to check and see if P runs to multi-function switch before i buy

 

is this looking at connector or coming out of switch