Keystone 5th-wheel trailer brake wiring?

norcal retiree · 09-07-2022, 06:31 PM

Just purchased a used 2011 Keystone Cougar 5th-wheel RV and hooked it up to my 2018 GMC 3500 for the ride home. That's when I discovered that my truck does not recognize the trailer hook-up and thus, no trailer brakes! Does Keystone use a different wiring pattern? Never had a problem with my older RV hooked up to the same truck. Any thoughts/ideas are greatly appreciated.

**JRTJH** · 09-07-2022, 06:57 PM

Keystone uses the "industry standard" umbilical plug wiring configuration. The brake signal is sent from the tow vehicle to the trailer on umbilical pin #2, the third pin counterclockwise from the indexing pin on the trailer plug. Ground is pin #1 which is the third pin clockwise from the indexing pin.

Probably the easiest way to determine if the trailer brakes are working is to jack one wheel off the ground, spin it and have someone pull the pin from the breakaway switch on the pinbox or a frame coupler. If that works, then focus on the umbilical cable/umbilical plug. If it doesn't work, then start troubleshooting the trailer brake wiring, hub/brake assemblies and magnets.

On a 2011 trailer in unknown condition, I'd suspect a bearing repack/brake inspection would be one of the first maintenance tasks. While there, check the date of manufacture on the tires. Almost every manufacturer recommends replacing tires at 5 years from DOM. You can find that date on the tire sidewall. It's a 4 digit number. The first two numbers are the week of the year and the second two are the year of production. As an example, 2012 signifies the 20th week of 2012. And 4710 signifies tires produced the 47th week of 2010.

norcal retiree · 09-07-2022, 07:04 PM

Thank you! At least I now know where to start. You rock!

norcal retiree · 09-11-2022, 01:27 PM

I'm not showing any voltage at the number 2 pin on the truck. Checked the fuse and it appeared to be blown, so I replaced it, but I'm still unable to detect voltage to the #2 pin. My guess is that I need to make a trip to the dealership.

**chuckster57** · 09-11-2022, 02:11 PM

Quote:

Originally Posted by norcal retiree

I'm not showing any voltage at the number 2 pin on the truck. Checked the fuse and it appeared to be blown, so I replaced it, but I'm still unable to detect voltage to the #2 pin. My guess is that I need to make a trip to the dealership.

Key in the “run” position?

norcal retiree · 09-11-2022, 02:14 PM

Yes, key in run position.

**chuckster57** · 09-11-2022, 02:22 PM

If you have a plug in the bumper and in the bed, I would trace the harness back to the connection under the bed.

norcal retiree · 09-11-2022, 02:31 PM

I'll take a look. Thanks for the help, much appreciated.

**JRTJH** · 09-11-2022, 04:31 PM

My 2015 F250 will not send a brake voltage to the umbilical unless the truck is in gear, engine running and wheels moving. Then, if I press the brake pedal, all I get is minimal voltage (the computer knows the truck is going slow enough that trailer braking isn't required. The only way I can "test my brakes at the start of towing" is to use the brake lever on the brake controller to apply "wheel locking voltage" to test the brakes.

That computer system in the truck is "smart enough" to know when to apply trailer brakes and when not to apply them. It's just "not smart enough" to know when I'm troubleshooting the system and when I'm towing the trailer....

You might find that the only way you'll get a voltage on the brake pin at the umbilical is with the truck in gear, engine running AND by pressing the brake lever on the brake controller, not the brake pedal on the floor.

**chuckster57** · 09-11-2022, 04:49 PM

I use a trailer emulator at work. It makes the TV think there is a trailer back there:

https://www.ebay.com/itm/14240040443...ee7fe6a8dd0996

norcal retiree · 09-11-2022, 06:26 PM

Good info, thanks. I'll give it a whirl.

norcal retiree · 09-11-2022, 06:27 PM

Ordered the emulator, thanks for the tip. Hopefully it'll help.

norcal retiree · 09-14-2022, 03:35 PM

While waiting for the emulator to arrive to verify the truck wiring status, I crawled around under the trailer to see if I can find anything. I discovered that at one time, in it's past, it had a tire blowout because the brake wiring for that wheel was noticeably longer and obviously had been replaced. Upon closer inspection, I found that the longer wires had been rubbing against the wheel and was almost severed in half. The edge of the wheel was polished like chrome from the wires rubbing. I'm guessing that's what blew the fuse on my truck?

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