Wireing when I hook up a trailer I don't have marker lights on the front half of any trailer but on the back half, marker, tail, stop, turn, and brake lights work. Why is this?????????????????? 2000 gmc sierra 1500

Your truck may have had the factory trailer tow package, but that did not come with a wiring connector in that year. There should be a wire harness under the rear of the truck near the center of the bumper with 7 wires of the following colors/characteristics -

Red/Orange - +12V Battery (Thick Wire) From fuse #8 (40A)
Black/Orange - Tail Markers (Thick Wire)
Light Blue - Trailer Brakes (Thick Wire)
Violet/Black - Backup Lights (Thin Wire)
Dark Green/Red - Left Stop/Turn - (Thin Wire)
Brown/Red - Right Stop/Turn - (Thin Wire)
Black - Ground - (Thick Wire)



Under the dash, the brake controller wiring should be -

Red/Orange - +12V Battery (Thick Wire) From fuse #8 (40A)
Black/Orange - Ground - (Thick Wire)
Light Blue - Trailer Brakes (Thick Wire)
White/Tan - Brake Light sense - (Thin Wire)

Hope this helps.

hope this helps

6 pin socket

6 pin plug

7 pin socket

7 pin plug

5 pin socket

5 pin plug

7 pin socket

7 pin plug

7 pin socket

7 pin plug

7 pin socket

7 pin plug

12 pin socket

12 pin plug

small 6 pin round plug & socket

1 tail, clearance - brown

2 left hand turn - yellow

3 right hand turn - green

4 stop - red

5 electric brakes - blue

6 earth - white

small 7 pin round plug & socket

1 left hand turn - yellow

2 reverse - black

3 earth - white

4 right hand turn - green

5 electric brakes - blue

6 stop - red

7 tail, clearance, side markers - brown

round socket

large 5 pin round plug & socket

2 left hand turn - yellow

3 earth - white

5 right hand turn - green

6 stop - red

7 tail, clearance, side markers - brown

large 7 pin round plug & socket

1 left hand turn - yellow

2 reverse - black

3 earth - white

4 right hand turn - green

5 electric brakes - blue

6 stop - red

7 tail, clearance, side markers - brown

7 pin round heavy duty plug & socket

1 earth - white

2 left hand rear , clearance and marker - black

3 left hand turn - yellow

4 stop - red

5 right hand turn - green

6 right hand rear , clearance and marker - brown

7 reverse/auxilary - blue

7 pin flat plug & socket

1 left hand turn - yellow

2 reverse - black

3 earth - white

4 right hand turn - green

5 electric brakes - blue

6 stop - red

7 tail, clearance, side markers - brown

flat socket

12 pin flat plug & socket

1 left hand turn - yellow

2 reverse - black

3 earth - white

4 right hand turn - green

5 electric brakes - blue

6 stop - red

7 tail, clearance, side markers - brown

8 battery supply - orange

9 auxiliaries - pink

10 earth - white

11 rear fog lamp - grey

12 auxiliaries - violet

We do not have the wiring diagrams. But here is the red neck method, use a 12 volt test light probe tool (any parts stores for $5) and as a friend operates each light circuit, probe the connector or harness and see what lights up, then mark the wire color and what it does, brake lights, turn signals etc.

Your vehicle CANNOT be wired for a trailer without using the converter box. The only vehicles that do not require a converter box are the vehicles that use the stop lamp bulb as a turn signal. Your vehicle is equipped with SEPARATE stop lamp and turn signal bulbs.

To make the converter box work correctly, it must be wired according to the instructions to BOTH the stop lamps AND the turn lamps. The tail (or PARK) lamps DO NOT go through the converter box.
Your trailer uses the SAME bulb for stop and turn - THIS is the reason you need a converter.

The wire color for both your LEFT TURN and your RIGHT TURN are LIGHT GREEN/TAN. Although the wire colors are the same at the bulb sockets, these are SEPARATE circuits and must be wired to the correct wire at the converter box. (LEFT and RIGHT) The converter box will have an INPUT connection for EACH of these.

The wire color for your STOP lamps is WHITE/TAN. The converter box should only have one INPUT wire that connects to this. It doesn't matter which side of the vehicle you connect this wire to. All of the stop lamps are on the same circuit.

The converter will then have only one wire for LEFT turn and stop (usually YELLOW) this is the wire that needs to go to your trailer connector for left turn and stop.
The RIGHT turn and stop will most likely be GREEN coming out of the converter.

you have the wiring crossed up

4 way flat molded connectors allow basic hookup for three lighting functions; right turn signal / stop light (green), left turn signal / stop light (yellow), taillight / license / side marker (brown) and a ground (white).brownwire will run both right and left side markers

White is ground, black is power to trailer battery trickle charge, blue is brakes, green is tail/running lights, red is left turn signal and left brake light, brown is right turn signal and right brake light, yellow is aux power/back up lights. This is the general color coding, there are exceptions, white, black, and blue are pretty much always as listed above, sometimes the others vary. If you find you are having trouble, post any further questions here, I'll be glad to help out. Curt

It sounds like your have may have your brake light and running lights crossed on your wiring harness to the trailer. Good luck and hope this help's

exactly what does it do? please explain what happens when you press the brake turn on the light than brake signals ect.....

In your wiring harness you have a brown wire, that is your tail and marker lights. The green wire is your right turn. And the yellow wire is your left turn. Don’t forget to add a ground wire. If you are installing a brake controller, run a blue 10 gauge wire to the trailer plug.