'03 T4R No Tail Lights or Dash Lights - Stumped - Help Please.

The tail-lights and dash-lights (illumination) on my '03 T4R recently went dark. The 10a fuse under dash (Tail) was blown and continues to blow every time I think I might have fixed the issue and insert a new fuse. Anyone experienced this? It's almost state inspection time and I need to figure it out.

What I've done:
Replaced all fuses both under-dash and under-the-hood
Sprayed the under-dash fuse block with electrical cleaner
Sprayed the under-the-hood fuse block with electrical cleaner
Pulled and cleaned the towing harness under the rear bumper
Pulled and cleaned the electrical harnesseses inside the rear hatch

It presents like a short circuit. I get tail-lights and dash-lights for the fraction of a second it takes for the fuse to blow. I do have flasher, brake and turn signals front and back. As well as headlights (high and low). The only issues are the tail-lights and dash-lights (meaning dash-illumination).

 

It sure sounds like it. Are there any signs of wiring having been pinched? Have you followed it all the way back?

 

Sure feels like this is a (hot) wire shorting to ground somewhere.

You could try to further isolate the problem by disconnecting one (tailight) connection at the back of the truck at a time. This will only help determine if there’s a problem within the lamp housing itself.

Next thing I would try is to remove the circuit fuse and go to each lamp connector, use a DVM to ‘ring out’ each hot lead wire to chassis. A dead short to ground will be quite evident and at least you’ll have a better understanding where to go next (follow the wire back to the fuse box)

 

I have inspected all the wiring I can see without disassembling the vehicle. No signs of any issues.

I was not able to identify where the short was taking place with an electrical tester. Probably need to get back after that and try a little harder.

Recent upgrades to my 4th Gen T4R included deleting the X-REAS suspension and replacing with standard shocks and struts. I checked to see if I nicked any wires. Saw nothing.

 

This is interesting! Studying the wiring diagrams for a 4th Gen T4R ... The Instrument Panel Illumination only functions when the Tail Light Relay is energized. Meaning a dark instrument panel is a nifty way of knowing your tail lights are out. Who knew?!

Now the misery ... If I do have a Tail Light Relay issue the Tail Light Relay is on THE BACK of the Passenger Compartment Fuse Box. Known only as R2. Sits between the Horn Relay (R1) and Power Relay (R3). Looking now for a tutorial on how to pull that fuse box. Looks like the dash will need to be removed first.

 

I did get the Passenger Compartment Fuse Box loose enough to get a look at the back. Found the four relays I was looking for. These 90987-02022 relays are also used in the AC system, and have been recalled/replaced with 90987-02028. Figured I'd replace these four recalled relays before starting the search for a bare wire.

 

@DS4Runner were you able to resolve your tail light / running light issues? Please provide an update. I am in the same boat as you and have become frustrated after trying virtually everything.

 

No resolution. Still no tail lights. I replaced the four relays on the back of the interior fuse block. That didn't help. I purchased a wire tracker probe to track down the fault and could not find any power coming our of the fuse block for the tail lights. I even pulled all the covers off the wires as they run along the door frame to the back and could not find any power going to the tail lights with the wire tracker probe plugged into the tail light fuse slot. My concern is that I have an issue within the fuse block. The only quick resolution I can come up with is installing a circuit and relay off one of the headlight fuses and running a wire back to the tail lights. That way when the headlights are on, the tail lights are on. Not ideal, but should pass state inspection.

 

Dang, what a pain in the butt. Thank you for sharing your experience. Been working on this far to long and I think I am at the same junction as you are. Not ideal but good idea installing a circuit and relay off one of the headlight fuses and running a wire back to the tail lights. Better than no running lights at all! SO FRUSTRATING!

 

@DS4Runner just to confirm, the relays you replaced were on the back of the interior fuse box located on the Driver Side? Think you mentioned passenger side above and I was not aware of a fuse box on the passenger side or its location.

 

Driver's side. No fuses on passenger side that I know of. You'll need to take apart the dash. Take lots of pictures as you do. Mark the screws accordingly. It is a bit of a puzzle to put back together.