ORP trailer wiring harness issue? Running lights not working

My new (200 miles) ORP using the flat-4 connector will operate the turn signals and brake lights but not the running (parking) lights. I connected to my trailer and my neighbor’s trailer with same response. I am reading 12 volts from the brake light pin to the ground pin. I’m reading an erratic 3-5 volts DC on the running light pin. I don’t know what the correct voltage should be but guessing 6 or 12. But the lights will not come on. The lights on the 4 Runner (brake, parking, turn signals) all work fine. That pin is adjacent to the ground pin. There are 2 wiring harness connections to the trailer receptacle. One for the flat-4 and one for the 7 pin. I can’t tell which clips to depress to remove the one I am interested in. They are so close together you can’t see both sides well. Anyone ever had this issue and know what the likely culprit is? I have a service appt tomorrow at 100 but I wish I could fix it myself. Thanks in advance

 

Let the dealer diagnose and repair it. It starts a paper trail for concerns down the road.

 

Agreed. It’s why I have the appt tomorrow. I just hope they take care handling the 4 Runner. Tomorrow it’s a week old.

 

What voltage do you get without the trailer hooked up?

 

I get 12 volts on brake light pin, to ground pin. Turn signals oscillate correctly. The running lights pin to ground is erratic 3-5 volts. I think it should be 12 volts. All these voltages are just using a voltmeter to the receptacle with no hookup placing the positive and negative probes accordingly. Black voltmeter probe always on ground pin

 

4 pin =yellow wire is left signal, green wire is right signal, brown is your running light and white is your ground. You can use a cheap 4 pin trailer wire tester from autozone to test at your pins or a regular 12v light tester from harbor freight to save the aggravation of hooking up to trailers to determine if it’s your vehicle or the trailer. If you confirm the problem is not your vehicle start with the ground wires on your trailer then the brown wire on your trailer. Im betting it’s not your truck that’s the problem but how the trailer wires are grounded but verify your vehicle first. Should only take 5 minutes with a tester. Good luck.

 

I don't think he needs a tester.

The voltage is low coming straight off his 4R. There is like 3 fuses for the trailer but I'm not sure if it would matter since its low and not 0. But you never know.

 

We hooked my neighbors boat trailer to my 4 Runner. Turn signals worked. Brake lights worked. Running lights did not. We hooked his truck to his trailer and everything worked including running lights. When I hooked my utility trailer to my 4 Runner, everything worked but running lights. Makes me think it is my new 4 Runner that has a problem. Especially since I’m not getting 12 volts on voltmeter with probes placed across ground pin and running light pin. Isn’t it true it can’t be a fuse since the 4 Runner parking lights work? I installed a trailer wiring harness in a Tacoma years ago and the wiring spliced directly into the wiring inside the rear taillight lens in parallel. There was no additional fuse involved. I assume the arrangement is the same just using plug-in connections.

 

No. The trailer circuit is separate. I know because an open lamp on my trailer blew the trailer circuit, and not my truck’s (conveniently actually).

 

Wow. Good to know. So it’s powered separately but it still needs the inputs from the brake light, turn signals and running light circuits. I guess they are just parallel circuits. So you are saying it could be a malfunctioning trailer receptacle fuse for the running light circuit only? Weird reading; erratic and low 3-5 volts. Even with truck not running, just accessory mode.

 

Would still be weird for a fuse issue to show as low-voltage.

 

Agreed. I’m hoping it’s a problem with the receptacle. It can be replaced easily. But if it’s not getting the input signal to turn on rear parking lights, that might be hard to troubleshoot. You should be able to unplug harness (feeding the receptacle) under 4 Runner, and read the voltage feeding the receptacle. I can’t figure out how to unplug the harness. Don’t want to break it. Usually you depress 2 opposite ears and it separates. It’s so close to the 7 pin receptacle you can see one side. Is that fuse block under the hood or near the parking brake?

 

I pulled that 30 amp fuse and it is blown? That’s why the running lights don’t work. Now the question is why is the fuse blown? Sounds like a short circuit? That may be hard to find? If I install a new 30 amp fuse and it blows instantly, the short is in my 4 Runner. If it does not blow and I measure 12 volts to ground at the receptacle, then I have a short on my trailer wiring. And it blew the first time I plugged it in.

 

An interesting but mostly annoying issue.

 

Well I swapped the 30 amp defroster fuse into the trailer running light location. Turned on truck with low beams on. I measured 12.43 volts on that running light pin. The fuse didn’t blow meaning there is no short in my 4 Runner. Awesome! Normally a blown fuse is black under the plastic and the conductor looks melted. This fuse looks incomplete but not blown. I either had a defective fuse from the factory OR a short on my trailer running light wire only. Not sure at this point but easy fix either way. I reinstalled the defrosted fuse and verified defroster still works. So I’ll pick up a few 30 amp fuses tomorrow. The fuse block under hood has 3 spares: 10 amp, 15 amp, 25 amp but NO 30s.

 

If you guys had not told me there was a separate fuse for the trailer circuit, I would not have learned what I did tonight. This forum is awesome. Thanks a bunch!

 

If we’re talking about boat trailers (I was), it’s possible that it only blows the fuse when the offending lamp is underwater.

 

My trailer is a utility trailer. But I tested my receptacle on my neighbors boat trailer since both are flat 4 pin connectors. So my trailer is never underwater. But you make a good point for boat trailers. The taillights are submerged for short periods.

 

Yup! And this prompts me to pick up a few spare 30 amp fuses!

 

I just picked up a 5 pack of Bussman low profile 30 amp fuses. $4.39. It’s identical in appearance to the factory supplied. Installed and it works.

 

Or very likely. Learned that one the hard way as well. I always disconnect my trailer lights now when launching my fishing boat. Which brings up the one gripe I have about my 4Runner. Why did they decide to put the connectors way down under the rear of the truck. Hard to easily reach without literally laying on the ground and they stand a chance of being submerged anyways.

 

I bought one of

$10 Jcase Fuse Kit Mini Jcase Fuse Assortment Low Profile 20A 30A 40A 50A 60A Fit for Ford Chevy/GM Nissan and Toyota Pickup Trucks Cars and SUVs

these and one of

Winlyn Automotive Car Fuses Kit - 272pcs Auto Blade Fuse Assortment Set Standard & Mini & Low Profile Mini (5A/ 7.5A/ 10A/ 15A/ 20A/ 25A/ 30A/ 40A) Car Boat Truck SUV Automotive Replacement Fuses

these to keep in my truck.

 

I personally thing the trailer fuses are rated too high or just don't want to pop.

I accidentally pinched by trailer lights behind a bolt when I was replacing some rusted parts a while back and nothing popped. But the wire sure melted.