Truck-side trailer wiring issues; all pointers would be appreciated

Hey y'all, let me preface that by saying, yes, I did use the search function, and yes I did read through many threads, and no I was unable to find, except for one, a thread that listed a similar issue.

BUT! I wanted to see if I could pick the brains of you fine TW people who have been around a lot longer than me. So, any help would be greatly appreciated.

Anywho, this is on a '17 TRD OR w/ factory towing package. I noticed on my trailer that my brake lights and turn signals were not working and the right light would occasionally just not work, "Okay Kaleb, check your grounds." went through each light made sure each ground had a good connection, checking with a DMM. The brake and turn signals still were not working so I started checking at the lights for power. I have power on the running light circuit (which I knew had power because, well, they worked) but I had no power on the brake lights or turn signals (with brake depressed and signals on) Soooooo I moved to the truck side of things. I picked up when of those plug-in testers for the 4-pin connector and it shows that I have power to the running lights but with any combination of hazards, signals and brake I have no power on the Right or Left brake/turn circuits and confirmed with a multimeter. Moved over to check the 7-pin connector and same thing. No power on RH or LH brake/turn. I checked the fuses in the truck, under hood and drivers kick, that I could find labeled towing and did not find any bad (however as I'm typing this I'm realizing I only did a visual not a resistance check, will go back and check tomorrow). I'm going to bring home my wire piercing leads for my multimeter from work tomorrow and check before each plug to see if I have power on that side or not. Wanted to reach out and see if anyone here has had this issue and could maybe point me into some checks that I may not have thought of yet. Electrical isn't exactly my strong suit. Injection molding is but that doesn't really help me that much here.

Any help would be greatly appreciated amigos

 

check 17 trd 1st without trailer being hooked up

then check to be certain however the trailer pigtail is connected

that it is correct ...............NOT shorted or grounded

check for side crosses & corrosion

if ALL is good U KNOW issues are on the trailer !!!!!!!

if everything truck + pigtail is correct leave Unconnected

check ALL wiring on trailer visually to be certain

wiring is NOT worn grounding inadvertently with frame o trailer

now hook up to trd & start trouble shooying trailer

 

It has been awhile since I messed extensively with the trailer wiring. From what I recall, the trailer left turn / right turn / brake lights are controlled by the combination meter (the dash cluster). The combination meter monitors for short circuits to ground, as well as shorts between the LH and RH light wires, etc.

My recommended first step is to disconnect the trailer, power cycle the truck, and see if the truck side is providing power correctly without being hooked up. Then ohm the truck. I bet you will find that the RH and LH trailer light circuits are shorted together.

The trailer tail lights are NOT controlled by the combination meter.

 

Stop/Turn Combo is inside the Combination Meter (not a separate module). If the Tow fuse is blown then no Stop/Turn on 4 pin or 7 pin Tow connector.

 

Wire piercing leads will screw you in the future -- moisture gets in the holes and corrodes the wire. Don't do that to your future self.

 

In case it helps here is the towing diagram. Looks like the turn signal/brake lights for the trailer come straight from the combination meter.

 

I've narrowed the issue done to being a truck side issue, not trailer but I'm all for triple and quadruple checking

I've got power to the running light circuit but absolutely 0v to the stop/turn on both left and right. Ill have to ohm between left and right, I havent checked that yet.

So the tow fuse is in the combination meter or is it straight wired?

noted, didnt really think too hard about that apparently.

Thanks for this, definitely going to save it and try to make some sense of it.

Thanks for the leads y'all! I can't spend a whole lot of time on TW since I'm at work but the combination meter are they fused there or straight wired from it? Do I need remove the whole dash or is this a case of removing the bezel and cluster and getting behind there? Or should I look at other things before resorting to that?

Thanks again everyone.

 

DON'T use a DMM to check for bad grounds, use a good-quality incandescent (an LED test light is virtually the same as a DMM in terms of what it will tell you) test light. A DMM will show ground even if it's poor, but by placing a load on the circuit, you can get a visual check on the "quality" of your ground.

 

I think the pic shows where the fuse is...

 

Got that, had already checked it but his phrasing made is seem as if it was inside the combination meter, which is what had me confused, but thanks.

Anyway, all fuses under the hood are good, all fuses under the dash on the drivers kick are good, every fuse labeled with any variation of "tow" has been checked good. The only thing I didn't check is the towing relay because, well I do not know how to test one without a power probe, but I imagine sense my running lights work, that should be fine, right? I pulled the 7-pin plug off the back side of the bumper and noticed quite a bit of corrosion on the pins, checked for voltage anyway and still did not have any power on RH/LH Stop and Turn. No pins seem to be shorted together either.

 

"His"? Who's phrasing?

Anyway, the module that handles the Towing combining of the STOP/TURN is part of the Combination Meter, it's not a part that can be removed. If it has failed then a new Combination Meter is the fix.

 

OP, with a Probe Lamp, verify TURN & STOP on these connectors.

TLT =Towing Left Turn
TRT =Towing Right Turn

 

T
hanks for the info man. Looks like my problem is the combination meter. I have no power at either connector.

Thanks for the replies everyone.

 

This could resolve your issue without buying a new Combination Meter...
Connectors C9 & C10 are on the Combination Meter.