Dodge ram 2500 with factory trailer harness/plug.

if you have a right signal on the truck and no signal on the trailer then you need to check the wire were it comes from the truck wire harness to the trailer plug. possibly a bad trailer plug also

Go to napa and they have the connectors that plug in to your existing wire connection, I don't know if they have the one for yours, but it won't hurt to check, you don't have to cut or splice the wireing with there trailer connectors, plug it in and done.

2004 Dodge Ram 2500 Truck Car Radio Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Pink
Car Radio Accessory Switched 12v+ Wire: Brown/Red
Car Radio Ground Wire: Black/Dark Green
Car Radio Illumination Wire: Orange/Dark Blue
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Dark Green
Left Front Speaker Negative Wire (-): Brown/Red
Right Front Speaker Positive Wire (+): Violet
Right Front Speaker Negative Wire (-): Dark Blue/Red
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown/Yellow
Left Rear Speaker Negative Wire (-): Brown/Light Blue
Right Rear Speaker Positive Wire (+): Dark Blue/White
Right Rear Speaker Negative Wire (-): Dark Blue/Orange

Well let me shed some light on this issue. I have the same problem. Trailer connection from truck does not have power to left turn signal and left brake light. I just got back from the dealership and $100.00 labor charge. My problem is the TIPM (Fuse Box for short) and FCM (little silver module hooked to the Fuse Box on the left hand side of the fuse box). $910.00 for the parts and Chrysler doesn't have any in stock. 4-6 weeks to maybe fill a back order. I am currently researching an alternative way to fix this issue. I will let you know.

You have got 7 pin trailer connector that was included in the optional trailer tow package. This trailer tow package also includes an electric trailer brake wiring provision that terminates at a connector located on top of the large body harness connection under the instrument panel to the left of the break pedal, as well as an electric trailer brake pigtail harness and an instruction card that are stored in the glove box when the vehicle is shipped from the factory. You will need to add an electric brake controller of your choice that will plug-in to the harness and that will also give you power on your auxiliary circuit.

Hey Boon,

The pinouts for a 7-way plug are as follows:
Seven wire Trailer plugs:

Horse, stock or utility trailers:
White = Ground - 1
Blue = Electric Brakes - 2
Brown = Tail and clearance lights - 3
Black = Battery, aux power - 4
Yellow = Left turn/Brake - 5
Green = Right turn Brake - 6
Orange or Purple (not both) = Auxilliary or Reverse - 7

Recreational Vehicle:
White = Ground - 1
Blue = Electric Brakes - 2
Green = Tail and clearance lights - 3
Black = Battery, aux power - 4
Red = Left turn/Brake - 5
Brown = Right turn Brake - 6
Yellow = Auxilliary or Reverse - 7

In both cases 4 is battery and 7 is reverse, aux or not used.

Double check your wiring using these lists as a reference.

Click here for my post on Trailer wiring

This should get us closer to the answer.

Best regards,
Mike

Check auto parts store or trailer place for adapter that goes into harness just behind bumper area, and "tees" into stock harness.

TPIM PROBLEM , MUST HAVE COMPUTER FLASHED AT DEALERSHIP

I have seen once before that the fuse box was bad on a 2003 Dodge 3500. I had power in and nothing out. We had to replace the box. Not cheap! Hope it is simple like a loose connection though. I think I had to pull the inner fender on the drivers side to access the bottom of the fuse box. Pain in the ****, but...

I'd get a 12vdc test light if you don't have one already & start from plug, and keep probing back from there. It may be as simple as a bad connection under truck where joined into harness.