Tail lights don't completely shut off

2010 Tacoma Sport, original owner, stock tail light assemblies. Stock tail light bulbs, after market reverse bulbs. Canadian truck with DRL.

I left truck running, head lights completly off (switched rotated completely off, not in between headlights on and completely off) and got out to check something. When the truck is running and the headlights off, there is still power getting to the tail lights, but not full power. I've owned the truck for 13 years and always thought when the headlights are fully off, so are the tail lights.

Is this normal? If it isn't normally, thoughts on trouble shooting?

Both sides are identical, only showing left side.

Truck off


Truck on, headlights off


Truck on, headlights on (either fully on or tail lights only position)

 

Is your brake light switch stuck on.

 

Something is back feeding. Usually see this with LED but not stock.

On that generation we are always suspicious of the trailer wiring harness, usually it pops fuses but who knows. Follow the trailer harness to the main harness and look at it carefully.

 

Curious if the camper top has an interior light?
If so, where is the power and ground coming from?
Does it have a rear brake light on top?

I'm not saying it's the camper top, but I've seen issues with poorly tapped confections on those.

 

No, I set up my phone camera and the brake lights are brighter than with the running lights on and the 3rd brake light comes on when brake peddle depressed

It does have an interior light, but that light is powered from a small battery pack (not connected to the vehicle electrical system at all). There is a 3rd brake light on the camper top that is tapped into the left rear housing of the truck. I will check it out, but the camper shell has been there for 13 years...the connect may be bad.

I did install LED license plate lights a few months ago, let me see if those are causing the feedback.

 

^^^ This. Many early 2nd gen trucks have either severely corroded connections or have been damaged by hitting something.

 

The LED third brake light on my ARE shell were still on after the truck was turned off. Not fully on, but still getting juice. I put a resistor between the LEDs and the truck electrical circuit, that solved the problem.
Mixing LEDs and stock lights can cause unexpected issues. I would disconnect the LEDs you recently installed and see if that solves the problem.

 

I'm getting 1.3v at the taillight when it should be nil. I pulled the LED reverse bulbs, no change. I pulled relay used to supply constant 12v to the trailer harness, no change. I pulled the fuses supplying power to the other pins on the trailer harness, no change. I pulled the taillight fuse, perhaps thinking the switch was faulty, but still had 1.3v at the taillight. I disconnected 3rd break light, no change.

I tried a few fuses, until I pulled the 7.5a accessories fuse, which resulted in nil volts at the taillight assembly. So something is going on with the accessory circuit and the taillight circuit. I do have LEDs installed in the cab to replace stock incandescents.

Installing a diode (or 2) to drop 0.7v each has crossed my mind, but not ready to give up yet.

Putting the tools away now. I'll try again next time.

 

I found the issue. I did the DIY heated mirror install, and I had the +ve for the LED in the switch connected to the +ve entering the harness, as opposed to tapping into the +ve (green wire) used to illuminate the display lights. Wire with the yellow heat shrink now connects to the +ve wire in the illumination circuit. All good now.