2004 Tacoma - No rear tail/brake/license plate lights

My 2004 Tacoma now has no tail lights, no license plate lights, and no rear brake lights. The center brake light on the cab works.The turn signals and hazard flashers work. Here's what I've done to troubleshoot;

• Pulled and checked, with an ohmmeter every fuse in the cab fuse block. All fuses are good.
  
• Pulled and checked, with an ohmmeter every small 2-blade fuse in the engine compartment fuse block. All fuses are good.
• Pulled the relay labeled "Tail" from the engine compartment fuse block, and brought it to my electronics workbench. I measured with an ohmmeter continuity through the coil. I applied 12V to the coil terminals and heard the relay click. When energized, the contact terminals show 0 ohms resistance, open-circuit when the coil is not energized.
• Reinstalled the "Tail" relay in the engine compartment fuse block, and heard it click when a helper turned on the parking lights with the cab control.
  
• Pulled the left taillight and disconnected the multi-wire connector to it. Turned on the parking lights with the cab control, connected a voltmeter negative probe to chassis ground (in case the wiring harness ground wire has broken), and looked for voltage on every pin in that connector. No pin had any voltage on it.
• Had a helper press he brake pedal, and confirmed that the brake lights do not come on, but the center cab brake light does come on.

Even though the "Tail" relay is good, I don't think the brake light circuit goes through it (how could it?). I thought the ground wire to the rear might be broken, but if it were, how can the rear hazard flashers and turn signals work?

And, to pre-answer the question, yes I have a 4-wire trailer light connector wired to the rear lights. My first suspicion is that it had shorted-out, causing a fuse to blow, but no fuses are blown.

I have exhausted my store of ideas. Does anyone have some suggestions?

 

What do read at the tail lights...lose of power or ground?

 

"What do read at the tail lights...lose of power or ground?"

I need to re-check tomorrow. I connected a digital ohm meter to a chassis ground point near the tail light, then touched the other probe to every terminal in the connector. All read close to 0 ohms, which I attributed to the other bulbs (front/rear) connected together.But I should see a lower resistance on the actual ground terminal, which would confirm that the ground wire in the harness isn't broken.

 

The evil converter Box might not have shorted but a open circuit is possible.

Physical Damage to the Harness to the harness from the cab to the rear causing a open circuit

Dash lights and front parking lights working correct ??

Good luck!

 

Where is the converter box, and how do I check it? I downloaded a wiring diagram; is the box shown on that?

I thought about that, but I don't know how to find the harness. Is it under the bed on the driver side?

Yes. Dash and front parking lights are working correctly.

--- Mike

 

Found it! I located the rear light wire harness, and discovered it runs through a kind of "tray" over a body member behind the left-rear wheel well, close to the spare tire.

I felt around and found two broken wires (there might be more). See the photo.


Squirrels are eating my Tacoma! The broken wires appear to have been chewed; see the marks on the left wire insulation. If so, this will be the second time squirrels have damaged the truck. Last year they chewed through the corrugated rubber hose connecting the fuel filler pipe to the tank. When I pumped gas, most of it would run out onto the ground! After replacing the hose, I surrounded that area with galvanized hardware cloth. Looks like I might need to do the same thing with the wiring. Bummer!

I hope I can splice the wires without a major hassle. It looks like the "tray" is held to the frame with two plastic clips, so maybe I can pop those loose and maneuver it around for better access. First I'll need to drop the spare time.

Thanks for all the suggestions. Add to the list: "Squirrels chewed the wires?"

--- Mike

 

I had something very similar and ended up cleaning a connector under the drivers seat and all became well. It’s the body harness connection to main harness I believe

 

Glad you found it easy! It is the Soy based insulation rodents find so enticing .

I think that falls under Physical Damage!