HELP! Tailights don't work with headlights on

I have a 2004 TRD Tacoma, with DTRL. When I go to turn the headlights on, the tail lights won't come on. The blinker works. The reverse works. The brake works. I have changed the bulbs in the housing. I have checked all fuses. I know that the license plate lights are linked in somehow(or so the manual says) to the tail lights. I have changed those bulbs as well. I have checked all known, and associated fuses. The damn things still won't work. I am not trying to get pulled over, and NEED SOME HELP OR TROUBLESHOOTING STAT!!! Anyone in Denver willing to help, I have beers waiting for you. Thanks.

 

Bump. Need to get this fixed ASAP.

 

Do you have a trailer towing harness? If so check the connections and see if one is broken.
There is a 10 amp taillight fuse and a 30 amp relay under the hood.

 

I lost my rear running lights a few weeks back and have yet to figure it out. Everything works Except rear running lights and rear license plate lights.

I have an '02 TRD and am in Denver debating who I can take it to and have figure this issue out. I checked all the fuses and relays- good to go. Appreciate a tip if you come across a solution.

 

There should be a ground wire attached to the frame somewhere around the rear bumper. Make sure it's not corroded off. Next, try another HL switch.

 

I have checked all the grounding wires......they are fine. I do have a trailer towing wiring harness(that I didn't install), and have checked the wiring on it, and whoever did it, did a great job F*ing it up. I am going to start there, and see where it goes. I have checked all fuses, and relays, and everything is good(as I had stated in the OP)

 

Check and see if you have taillight power going into the trailer tow converter box,then see if there's power coming out of it. I've seen these converter boxes cause lighting problems.Hope this helps.

 

Now we are cooking. Never thought to do that. Thank you sir.

 

A buddy of mine has an 02 4 runner that was having light problems it was indeed the trailer convertor box causing all of his problems,the box was actually warm to the touch. So we wired in a new convertor box and all lighting problems were gone.

 

FIXED. I went over to a buddies house, and we found the wiring(from previous owner, or topper shop) had wired the trailer wiring to the back left of the tail lights, etc. The little plastic "Sawyer" crimps is what they are called, had broken the wires in multiple spots. Went to the local hardware store, paid $.46 for 2 feet of 16ga multi strand, and boom, problem solved. Even got the wiring fixed the lights in my camper shell. All the fuses were fine, bulbs were fine, and then finally made it to the back of the truck, and looked underneath where the wiring was done, and found the bad line. Thanks for all the suggestions. Much appreciated.

 

Glad to hear ya got it fixed,sometimes electrical is a pita!!!!