L8000 turn signal wiring diagram, turn signals not keeping power traced power supply but cannot find correct relay , they work periodically when u slam the hood

many lighting systems use two flasher relays to isolate turn signal function from hazard function. each has an independent power supply source path or circuit. you'll need to trace power to the bulbs from the turn signal switch, and from the fuse boxes to the switch.

Did you look at wiring diagrams to see if all of these have anything in common ? Ground connection , B+ power supply etc..... Then testing the circuit's with a DVOM - digital volt ohm meter . Voltage drop testing .
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Did you replace the indicator flasher relay in AUX relay box 2 ?
Free wiring diagrams here http://www.bbbind.com/free-tsb Enter vehicle info. year , make , model an engine size. Under system click on lighting ,then under subsystem click on turn signal lamps . Click the search button then the blue link.
Track it down , where do you have B+ an don't .

This may sound confusing, so here goes.
Normally I would say check the turn signal switch because for decades the brake light switch power went thru the turn signal switch.
But in your case, its more complicated.
The wiring diagram looks like you have a wire from the brake switch and another from the turn signal that joins inside the right and left rear tail lamp assembly. There are also fuses in the rear fuse box including one for just the brake lights. So its possible that fuse is dead and yet the turn signals would work.
You may have to get a book with the wiring diagrams to trace the circuits.

I'd check your multi-function switch (on your steering column, what you touch to turn your turn signals on). There is a small metal clip on the base of it that tells your car to turn the turn signals on (right or left). Also trace the wires from the mulit-function switch to your turn signal relay and see if you're getting power when the switch is activated.

Have you tested out the fuel pump? check for plugged fuel filter?
plugged fuel lines to the fuel rail, injection pulse at the injectors? power to the fuel pump relay? grounds needed to make certain systems work must check those also. get a wiring diagram of the fuel supply system and back trace all the wiring and see if you have power and ground and signal.

Turn signal switch (also brake light canceling switch) most likely bad or bad wire to it or from it. Check, with key on run, for power into switch. Turn switch on, check for power out. No power out switch bad. Power out, trace to rear tailight harness for broken wire.

CHECK TURN SIGNALS BULB SOCKETS THEY HAVE BEEN KNOWN TO SHORT.

If your hazard lights work you need a turn signal switch, If hazards do not work replace the Flasher module

Check fuses, relays and body control modules (in that order.) If necessary get a good wiring diagram and trace systems back to see where shared power is supplied.

RELAY, NOISE SUPPRESION/is 1323592 its black and mounted under the hood on the shock tower, check page 4 and page 16 under LHB230FT in your book(item 464) ? why are you messing with this relay if you have a light problem ? does left turn signal stay on with key off /with parks only /with head lights /both front and back turns or front only? have you removed both frt and back bulbs together and ck voltage in sockets ?/wrong bulbs? i would need more info