At a loss with trailer wiring harness

[REW]

Someone has downloaded all of the appropriate Toyota service manual documentation for your 2006 Toyota Tundra as follows:

https://drive.google.com/file/d/0B-5...VhOGtKWjA/view

If you scroll down to page 4023 and page 4024, there is a very good print of the vehicle lighting schematic with the towing converter.

As one can see on page 4023 - the towing converter that is in the glove box area - works only on the brake and turn signals for the trailer.

The tail light comes through a different source - right off of the rear vehicle tail lights.

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If you want to do a simple fix - without dealing with the factory towing converter, you could install a towing converter in the rear tail light assembly of the drivers side of your vehicle.

At that position, you have access to the right and left turn signals as well as the brake signals.

You pick up a source of 12 volt power, and then run the signals into an after market converter and rewire your factory tow connector.

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But, if I were doing it, I would remove the towing converter, verify that you have + 12 volts going to the converter and if you do not have 12 volts coming out of the turn signal and brake light wires when you activate the turn signals or brakes, I would replace the factory converter with a new unit.

If you do not have +12 volts going into the converter, I would replace the fuse and or wiring that feed the +12 volts to the converter.

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After looking at the factory wiring schematic in the links posted above, the wiring is quite simple and straight forward.

Good luck

p.s.
Don't print out the 4,000 pages of the link. However, you might want to down load the 4000 pages to your laptop, so that you could take the lap top to the truck to work on the vehicle with all of the factory information at your disposal.

[Willey walleye]

REW: Thanks to all your help and the diagrams, I was able to find the problem (I hope). I took off my glove box and my front console and was able to test the towing power converter, and it appears to be the problem. I'll order a replacement and install it when it gets here. I'll keep you posted.

P.S. - Much obliged for the tundra service manual, that thing is an amazing resource.

[U D]

Did you test the fuses by checking the Continuity with your meter or just by looking at them? Isolate the fuse from the circuit and check continuity with your Volt meter set to Ohms. Fuses can look good but be bad.

[Willey walleye]

Originally Posted by U D

Did you test the fuses by checking the Continuity with your meter or just by looking at them? Isolate the fuse from the circuit and check continuity with your Volt meter set to Ohms. Fuses can look good but be bad.

I did check the all fuses with my multimeter. There was one towing fuse that I couldn't check with the meter as it is in some plastic case and I couldn't remove it. The only way I think I could've gotten it out was with a pliers, but being as other fuses that control functions of the engine were in that same housing, I didn't want to risk braking it. So that fuse got a visual inspection only.

[Agronomist_at_ia]

Originally Posted by Huntindave

Agreed, my SOP is replace fuses once,,,,,,,,,,,,,,,,, if it happens again, locate the cause.

Wasn't it a few years ago some guy down south used a 22 shell has a fuse since he didnt have any.......then after he drove for awhile the current set the shell off shooting the guy in the leg.....

You can always try the WTF? and just put a bigger fuse in........

[Willey walleye]

Still waiting for the part to arrive.

[wellpastcold]

Give us an update when you get it. I would be interested to know how you made out.

[Willey walleye]

Got the new (used) power converter and installed it. Same thing as before. No signals or brakes. Multimeter tested the leads to/from the converter box and same results as before....No power at the signal and brake leads. So it's looking like the problem is somewhere between the converter box and the beginning of the wiring under the hood.

[REW]

Willey,
Look in the manual and find the source of your turn and brake signals.

Normally the brake signal will come off of the switch that is connected to the brake pedal.

Normally the turn signals come off of the turn signal flashers.

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But, as I said earlier, you can take an after market box, put it in the driver's side rear tail light area - find the left, right turn signal and brake signal in that part of the truck and connect to the after market converter box. You will have to have a fused source of +12 volts to power the converter box as well.

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By the way, when you use the multimeter to check the input voltages going to the glove box converter that you just changed - did you have the source of + 12 volts?
Did you have either right, left turn signal or the brake light signal?

Take care

[DW]

This is a similar problem I had with a Jeep GC. I was able to conclusively narrow the problem to the vehicle, not the trailer although the problem started with a trailer short.

I discovered an inline fuse had blown located near where the factory aftermarket wiring harness connected to the battery. There was no way to know the fuse was there or that it was blown. I found it because I started to unravel the wiring harness for testing because I suspected a harness problem. Look for a bulge in the wiring harness for an inline fuse.