Possible trailer plug/adaptor problem

[OR VietVet]

All my turn signals and rear lights work on my 2005 Z71. I have a tow plug adaptor that when I plugged in to the round plug at rear converts to a 4 pin or 5 pin plug for towing a trailer. Intermittently, when using that adaptor, the right side trailer lights do not work. No turn signal, no brake light and no taillights. I have used two different adaptors with the same results. I think that since all my vehicle rear lights work, I need to dig in to the tow package round plug at the back of my bumper. I am ruling out a junction block problem for the reasons I have listed. I have not looked yet. Is there a set of vehicle wires from the block to the rear vehicle lights and a separate set of wires from the block to the tow plug?

 

[Mudsport96]

It could also be in the trailer wiring as well. Bad ground, loose power wire.

 

[S33k3r]

Test your trailer plug first. If nothing, test your trailer wiring. More than likely you just have a loose wire/connection somewhere, and my money is on the trailer. From what little research I have done, the trailer plug tends to be binary; it either works or it doesn't.

 

[Fless]

The harness to the back side of the 7-blade is removable, if you get that far checking contacts.

Not that it's your problem, but I replaced my connector with a Hopkins 40920 so I'd have the 4-pin connector when needed. It's plug and play, and a physical twist install into the OE mount on the hitch.

Endurance™ Multi-Tow® GM Twist Mount 7 Blade and 4 Flat Connector

 

[OR VietVet]

More story details. I have no trailer but I do move some trailers around for my friends and I do some work on trailers in my driveway, like wheel bearing pack, and move trailers here to do that work. The right side problem is constant. It happens with any trailer I hook up.

 

[Mudsport96]

More story details. I have no trailer but I do move some trailers around for my friends and I do some work on trailers in my driveway, like wheel bearing pack, and move trailers here to do that work. The right side problem is constant. It happens with any trailer I hook up.

Ah a Paul Harvey moment lol. Well if it is multiple trailers, I guess yes it could be the connector or tahoe wiring.

 

[OR VietVet]

Ah a Paul Harvey moment lol. Well if it is multiple trailers, I guess yes it could be the connector or tahoe wiring.

Gonna inspect tomorrow. Right now is 60 degrees here but tomorrow about 10 a.m. is supposed to be the same at 60 degrees. Gonna take advantage of the nice weather and crawl around and check wiring while my girl is here to run the lights inside the rig. I have not had to deal with that junction block before. Is the spare tire in the way and I am gonna have to drop that tire for access or can I work around that tire or the block is easily accessible and tire is not in the way?

 

[Mean_Green]

Dig into the trailer wiring harness itself going to the connector. I found several wires corroded completely off. I had to cut a couple of them a few inches back and splice new wires on.

The connector itself was toast. I replaced mine with a Curt 57102 that gives the round, a 4 way flat and a backup alarm (that some people hate with a passion). I wanted it to let people know to look out because I probably can't see them.

Note, there are two wiring configurations for 7 pin connectors. One for utility trailers and one for RVs. I have no idea why, but you can make it work for either.

 

[Mudsport96]

Gonna inspect tomorrow. Right now is 60 degrees here but tomorrow about 10 a.m. is supposed to be the same at 60 degrees. Gonna take advantage of the nice weather and crawl around and check wiring while my girl is here to run the lights inside the rig. I have not had to deal with that junction block before. Is the spare tire in the way and I am gonna have to drop that tire for access or can I work around that tire or the block is easily accessible and tire is not in the way?

I think most stuff back there is easier to access with the tire out of the rear

 

[Donal]

Dig into the trailer wiring harness itself going to the connector. I found several wires corroded completely off. I had to cut a couple of them a few inches back and splice new wires on.

The connector itself was toast. I replaced mine with a Curt 57102 that gives the round, a 4 way flat and a backup alarm (that some people hate with a passion). I wanted it to let people know to look out because I probably can't see them.

View attachment 400486
View attachment 400488

Note, there are two wiring configurations for 7 pin connectors. One for utility trailers and one for RVs. I have no idea why, but you can make it work for either.

RV's require a full time 12 volt connection to power low voltage systems like lights, and to charge rv battery and applicances.

 

[Fless]

Also keep in mind that the trailer lights are on circuits that are separate from the lights on the truck body. Separate trailer fuses for left brake, right brake, and running lights.

 

[OR VietVet]

Also keep in mind that the trailer lights are on circuits that are separate from the lights on the truck body. Separate trailer fuses for left brake, right brake, and running lights.

Before I start poking around, where are the fuses for the trailer lights? In the same fuse box as the truck lights? I was gonna look at this yesterday but grilling took over. With the Xfinity and Cup races on today, it is not gonna happen today either. I will be working on my neighbor's trailer this week and will look at the lights problem then, when I have a trailer to hook up to and verify everything. Thanks, @Fless

 

[Fless]

Before I start poking around, where are the fuses for the trailer lights? In the same fuse box as the truck lights? I was gonna look at this yesterday but grilling took over. With the Xfinity and Cup races on today, it is not gonna happen today either. I will be working on my neighbor's trailer this week and will look at the lights problem then, when I have a trailer to hook up to and verify everything. Thanks, @Fless

In the underhood fusebox. The underside of the lid should have the diagram for the layout.

 

[OR VietVet]

@Fless, I did find a blown 15 amp mini fuse that was marked as TRL PARK and replaced it. I also found an ok 15 amp TRL BU. Replaced the blown fuse and now have brake lights and headlight/park lights and left turn signal but still no right turn signal. The right turn signal has been the constant, as the one that does not work. Both of the 7 pin adaptor plug ins have the same, no right turn signal problem. Further digging required.

 

[OR VietVet]

Dug in a little deeper today. The back of the trailer wire 7 pin plug in is loaded with crap and the junction block has a crack in it. Luckily my Tahoe lights all work. I ordered in a replacement Genuine GM junction block. It was located directly above the tailpipe about a foot up on the inside of the body. Looks to have a clip that you stab in and then a bolt at other side. I also ordered an ACD 7 pin harness assembly and I ordered a Curt bayonet mount assembly for the harness. It does not bolt into place, it stabs thru the mount hole and you turn it and it locks into place. Will be doing a complete cleaning and re-tension of all plug in connections at the block.

 

[Fless]

Dug in a little deeper today. The back of the trailer wire 7 pin plug in is loaded with crap and the junction block has a crack in it. Luckily my Tahoe lights all work. I ordered in a replacement Genuine GM junction block. It was located directly above the tailpipe about a foot up on the inside of the body. Looks to have a clip that you stab in and then a bolt at other side. I also ordered an ACD 7 pin harness assembly and I ordered a Curt bayonet mount assembly for the harness. It does not bolt into place, it stabs thru the mount hole and you turn it and it locks into place. Will be doing a complete cleaning and re-tension of all plug in connections at the block.

I should have offered my OE 7-blade bayonet mount connector (no harness); I replaced mine a while back with a PnP Hopkins. Well, if anyone needs one, it's available for the cost of the ride.

 

[Doubeleive]

you can always test the pin's on the trailer connector with a meter at any time to verify operation, a trailer is not necessary
there are diagrams online that show which pin is which, left/right/brake/power, etc

 

[OR VietVet]

you can always test the pin's on the trailer connector with a meter at any time to verify operation, a trailer is not necessary
there are diagrams online that show which pin is which, left/right/brake/power, etc

The flip cover on the 7 pin has the wires/connections all identified. You should know by now that I don't piece things together. I just replace parts that don't meet my standards.

 

[Fless]

Dug in a little deeper today. The back of the trailer wire 7 pin plug in is loaded with crap and the junction block has a crack in it. Luckily my Tahoe lights all work. I ordered in a replacement Genuine GM junction block. It was located directly above the tailpipe about a foot up on the inside of the body. Looks to have a clip that you stab in and then a bolt at other side. I also ordered an ACD 7 pin harness assembly and I ordered a Curt bayonet mount assembly for the harness. It does not bolt into place, it stabs thru the mount hole and you turn it and it locks into place. Will be doing a complete cleaning and re-tension of all plug in connections at the block.

Update? Wondering if this fixed the issue.

 

[OR VietVet]

Update? Wondering if this fixed the issue.

I got the new GM junction block and installed it. I cleaned each wire/connector and used dielectric grease during the reinstall and did find another blown 10 amp fuse at the fuse block at driver's side of the dash and now all works as should. Sorry for the delay on the results.