1999 GMC Sierra Trailer Plug-No Power

DCRUZE

MEMBER
1999 GMC SIERRA
V8
2WD
AUTOMATIC
80,000 MILES

I have a factory round 7 pin trailer plug installed on my truck that is tied into the wiring harness. It has no power running to it. I checked every fuse that I could find and they are all good.

Any ideas on what else to check?

Wednesday, November 4th, 2009 AT 7:04 PM

5 Replies

JDL

MECHANIC
16,098 POSTS

Welcome to the forum, do you need wiring colors at the connector? The above info shows trailer fuses and location. If the fuse circuit isn't hot, it's a dead circuit, even if the fuse is good.

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Thursday, November 5th, 2009 AT 11:19 AM

DCRUZE

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3 POSTS

I checked the power going to each trailer fuse with the engine running and the head lights turned on. The fuses are OK, but there is no power on either contact in the fuse box.

Any other suggestions on what to check?

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Thursday, November 5th, 2009 AT 3:34 PM

JDL

MECHANIC
16,098 POSTS

I need the wiring colors at the trailer connector. I'm having trouble finding what I need. The label in the fuse box doesn't match up with the power distribution wiring diagram. It is possible there are some circuits for the upfitter that aren't being used.

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Thursday, November 5th, 2009 AT 4:26 PM

DCRUZE

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Sorry it took me so long to get back. The wiring colors at my trailor plug are:

Red
Black
Green
Blue
White
Yellow
Light Green

and a Light blue that hangs outside the plug. I think this might be for a trailor brake.

If it helps the vin # on the truck is 1GTE19VXXZ531505

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Tuesday, November 10th, 2009 AT 12:45 PM

JDL

MECHANIC
16,098 POSTS

Hi, the databases I looked at, all the wiring colors don't match? Red wire should be hot all the time, according to my info. I've had trouble trying to track the red wire, I looked at trailer circuit and auxilliary power supply. There should be mega fuse block, under hood, passenger side, close to battery, check there. Also, check auxilliary power center, center of dash, under the heater controls.

Yellow wire is left turn, dark green wire is right turn, White may be brake lites? Not sure about the others?