Troubleshooting Trailer Wiring With 2002 GMC Sierra 1500HD

Question

Question:

I have a curt installed already. Problem I have is all signals work on both 7 and 4 position connectors using a meter and connected to my LED single car auto-transport trailer. I have a old bulb trailer that using a 12v battery all lights work. But if I connect bulb trailer to truck no bulb lights work. I tried jumping a bulb across LT/brake to ground on truck and bulb light doesn't work, no voltage. Bulb trailer has worked for over a year, acts like curt can't supply current?

asked by: Jeff

0

Expert Reply:

There are taillight converters available and it is possible I can find something to work for you though I would need to know the year of your GMC Sierra 1500 in order to find out. If you can get back to me with that information I can try and find a solution for you.

expert reply by: Kyle S

0

Jeff

1/25/2018

I have a curt installed already. Problem I have is all signals work on both 7 and 4 position connectors using a meter and connected to my LED single car auto-transport trailer. I have a old bulb trailer that using a 12v battery all lights work. But if I connect bulb trailer to truck no bulb lights work. I tried jumping a bulb across LT/brake to ground on truck and bulb light doesn't work, no voltage. Bulb trailer has worked for over a year, acts like curt can't supply current?

Reply

Kyle S.

1/25/2018

From your description, since the lights work on your trailer with LED lights but not older, incandescent lights it sounds like there may be a short in the wiring which is causing the issue; a harness should be able to supply enough current to your lights. The lights work when connected using a 12V battery but that could be enough direct current to circumvent a short so that is going to be the first thing you'll want to look for. If you have not already you are going to want to test the connector on that trailer as well. Another issue you will want to take a look at are the ground connections, as they can be the cause of numerous lighting problems. You'll want to make sure your grounds are securely attached to bare metal surfaces free of any paint, dirt or corrosion of any kind. Also check your wiring thoroughly to ensure there are none that are crimped, broken or otherwise damaged. If possible, check and see what amperage your Curt harness is rated for because it is possible that you are overdrawing. You can also remove some of the incandescent bulbs and see if it works after that, which would also indicate an overdraw. I've added links to a pair of help articles on trailer wiring that you may also find useful and if you cannot find the issue after doing this troubleshooting let me know and we can continue to work on the issue.

Reply

Answer 1

If your Envoy brake lights stopped working along with the trailer's brake lights and you know the vehicle brake circuit fuses are good then the issue is likely to be related to the connector for your wiring harness. The 4-pole and 7-way harnesses…

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Answer 2

Most GM trucks use a pretty standard wire color for their tow packages, but I always recommend testing for function, and not just color. If you follow the bundle back there should be more wires than the ones you mentioned, for a total of 8.…

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Answer 3

The first place I would check is the fuse box. The trailer turn signals and trailer running lights are all on separate circuits. The fuse box under the hood is where they are located, and they are in the front closest to the stud on the right side.…

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Answer 4

The closest grease caps we have available to the 2.04 inch hub bore diameter you provided are the Bearing Buddies #BB2047. These are designed for 2.047 inch hub bores so they should work great. They will replace the existing grease caps and provide…

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Answer 5

I can help you determine the functions of the wires in the bundle you sent in a picture of by testing them with a circuit tester like part #PTW2993 but we don't have a way to identify them just based on color. So have a buddy apply the various…

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Answer 6

If your trailer has separate turn signals from the brake lights and you want them to remain that way, you will need to use a special converter. On the trailer side, behind the 7-Way, you will attach the Vehicle to Vehicle Taillight Converter,…

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Answer 7

The difference between the Class II and Class III hitches has to do with their Gross Trailer Weight (GTW), their Tongue Weight (TW), and their Hitch Receiver Size. Class II trailer hitch receivers have a 1-1/4 inch receiver and can be rated up to…

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Answer 8

A 4-Way trailer connector has the basic lighting functions only; running lights, left turn signal and brake lights, right turn signal and brake lights, and ground. A 7-Way has these functions and a 12 volt circuit, a circuit for electric trailer…

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Answer 9

There is only one difference between the Curt Trailer Hitch Receiver #C13176 and etrailer Trailer Hitch Receiver #e98909 that fit your 2020 Chevrolet Colorado, which is the finish. The Curt trailer hitch has a glossy black finish while the etrailer…

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Answer 10

The OEM prep package consists of 4 "pucks" in the bed of the truck that will allow you to drop in puck style hitches for easy installation and removal, that gives you a completely clear bed when not in use. The B&W Companion OEM 5th…

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Answer 11

It could be a tow package fuse on the vehicle. Use the owners manual to find the locations of fuses/relays related to the tow package wiring to check them and replace as needed. If the issue is not a fuse or relay then you can test the vehicle side…

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Answer 12

In order to determine the torque rating for the lug nuts on your trailer you will need to know check out the chart I attached that shows all of the torque specs for all the trailer lugs available based on stud size, wheel material and wheel size.

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Troubleshooting Trailer Wiring With 2002 GMC Sierra 1500HD

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