Directionals and Brake Lights Pins in 7 Pin Trailer Port Not Working

I had a wire come loose on my trailer when towing which created a short. I fixed the wire but since the short, there seems to be an issue with my truck. The directionals and brake lights pins in the 7 pin trailer port are not working. I've tested them with a volt meter and got nothing. I've checked the fuses in the engine compartment and they appear to be fine. The running lights pin works fine. Is there a relay or module somewhere in the truck that might control only the directionals and brake lights? Thanks in advance!

 

Did you check the fuses in the cab behind the dash up above the driver side kick panel??

 

Yes, I've checked all the fuses and relays to include the ones under the dash. I went to a UHaul place and they checked my pins and confirmed that there is no power to the brake lights or directionals. The guys mentioned that the wires sometimes go straight to the ECU and that my issue might be in the ECU and I'll have to go to a dealer. Considering my fuses and relays are good, is there somewhere else I should check and can anyone confirm the validity of the issue potentially being in the ECU?

 

I think you'll need to look at the wiring schematic and trace the wires back to the power source. It's very unlikely that it would come directly from the ECU since computers aren't designed to handle that kind of power. I remember someone posting it here a while ago but I'm not sure when. Hopefully they will post it again or a search will find it.

 

That 30A “Towing” fuse and the J29 flasher relay are the first places I’d be looking.

 

Thanks. I've checked the 30A Towing fuse and I several relays. Not sure if one of the relays I checked was the J29. I'll start tracing wires and let you know what I find.

 

Of note, all my directionals, brake lights, and everything else works fine on the truck. I believe the J29 relay controls the truck's directionals. If the truck directionals are working fine, then shouldn't that indicate the J29 relay is fine?

 

Good catch on the J29 flasher relay, but it is different outputs so I wouldn’t eliminate it being the cause on that alone.

How did you check the 30A towing fuse? Visual only? It really should be your issue based on the cause being shorted wiring, so if you haven’t tested for voltage on both sides, or removed it and tested with an ohm meter, I’d strongly recommend that. And make sure it’s in the correct location.

 

Ok, thanks. I'll check the J29 Relay in the next couple days.

I checked all the fuses with a volt meter. I didn't removed them but just touched both sides of the fuse with the volt meter probe to ensure current was passing through them. All were reading +/- 14 volts on both sides.

 

@bravo46 Hi... I had an issue towing my boat a couple weeks weeks ago, towing with my 4runner. After freaking out for a few minutes 100 mile from home, I asked myself.. "isn't this a Toyota?". I went to the local Napa, borrowed their test light and then bought a new 7 pin to 4 pin adapter and I was on my way.

I realize this doesn't sound like your issue. However, I went out to look at my Tundra and asked the same question. Since you already checked the fuses....
1. Do you have power for the directional and brake lights on the adjacent four pin connector?
2. Does it have factory tow wiring (I'm not sure if they all do or not)? Maybe one of the connectors near the bumper is loose. If aftermarket, maybe there is another fuse hidden near the bumper.
3. It seems unlikely that faulty wiring on your trailer would cause a major catastrophe to the truck or ECU.

 

1. Neither the 7 pin or the 4 pin connectors are working. Same issue - it has running lights but no directional or brake lights.
2. I believe it has factory tow wiring. I looked for another fuse near the bumper.
3. Looking at the wiring diagrams, I agree. I'll let you guys know what I find.

 

The flasher relay looks to be the most likely issue since it handles both the turn and brake signals. You should be able to unplug it and check the inputs. The red wire would have power on it when you step on the brake pedal. The green/ light green will have power on them when you turn on the ignition and use the turn signals. You could unplug it and jumper between the gray wire (30a power) and either the yellow (left brake light) or red (right brake light) wires. If the trailer light works it's the relay.

 

Thanks! So update. I removed the flasher relay amd tested the wires in the plug. They appear to work fine. If I use a wire to jump from a hot wire to the trailer directionals, i get power at the trailer plug. When plugged in, it appears only one of the brown relays in the circuit board is working. I've ordered a new flasher relay module and hopefully that resolves it. Ill keep you posted.

Fyi, rockauto.com has great deals on parts. I paid $38 for the flasher module. Everywhere else it was between $50-80.

 

Fixed! BLUF, it was the 30A towing fuse which had been placed in the empty slot right below (Apparently this empty slot also has power which is why the fuse kept reading good and I didn't pick up on the slot location. My brother or I must have moved it when fixing the broken trailer wire on the highway. I realized I hadn't tested the gray wire to the flasher relay and found it didn't have power so I went back to the fuse and after staring at it for awhile and testing it several times, discovered it was in the wrong location. I moved it up and now everything works. Guess I'll cancel my flasher relay order! Thanks all for the help.

 

Well, I do know from experience how that very thing can lead a guy on the wrong direction. Glad you got it figured out.

 

Welcome from NY.

 

Although I did not have a short, I am experiencing a similar issue as the initial post, running lights work but no brake or turn signals, on my recently acquired 2021 Tundra.
"I've tested the 7 pin with a volt meter they work fine. I've checked the fuses in the engine compartment and they appear to be fine. The running lights pin works fine. Is there a relay or module somewhere in the truck that might control only the directionals and brake lights?"

I have Ohm checked all fuses and locations numerous times. I wish mine was as simple as fuse in wrong location.

I have had this trailer 12 years and it has always worked fine through two Tacoma's.

New here and first post. Appreciate any and all suggestions.

I was waiting to post this until I did a few more checks..
NEWS FLASH- Solved

I tried plugging the the trailer into my 4 Runner and it worked fine all running, brake, and turn signals.

Attached trailer to Tundra again and experiencing the same no brake / turn signals.

Discovered that the lights must be on for the towing brake lights and turn signals to work. Quite a bit of time invested but all is working fine now. Proved it by turning off the lights and then the trailer brake lights and turn signals stopped working. Lights on and all works fine. Subtle message they want your lights on when towing I guess?
Anybody else have this issue hope this helps.

 

Turns out all is not OK. Thought this was easily resolved in my last post but discovered just prior to my last trip a strange situation.

A quick run down.
Tundra 2021 1794 Edition
As the truck sits running, all lights work: running, brake, turn signals L&R, and hazards

Plug 7 pin trailer into truck HITCH NOT ON BALL now:
running Yes
brake Yes
turn L&R blink only twice
hazard blink only twice

Plug 7 pin trailer into truck but ON THE BALL now:
running Yes
brake Yes on truck NO on trailer
turn L&R NO on truck NO on trailer
hazard NO on truck NO on trailer

Trailer is all aluminum 13 years old and has been garage kept. It has worked fine until I got this Tundra
Trailer all functions worked on
1993 4 Runner
2009 Tacoma
2014 Tacoma
2019 4 Runner
Tested on 2021 Tundra of my neighbor

Any help appreciated

 

hey lucky, did you ever figure this issue out, Im having the same issue, no r/s turn signal at the 7 pin, truck blinks once, but works fine if the trailer is not connected.