fallen1948

I have a 2003 Dodge Ram 2500 diesel with towing package and the pin on the tow plug for the left brake light doesn't work. Does anyone have any suggestions on what the problem could be.

grouch

Do you have the 4 or 7 pin plug? Does your left brake light on the truck work? Left turn signal? I'd check the wire connection at the plug first and then at the harness. If you have screw connectors at the vehicle plug end, you may have some corrosion on the connection not letting current through.

fallen1948

It's a 7 pin plug and the truck lights all work. I've checked the wires going into the plug and it all looks ok. I'm not sure if the relays could be the problem or not. Where would I get a wiring schematic for the trailer plug harness. Thanks for your help.

Colo_River_Ram

Have you checked the fuses, the trailer plug has separate fuses for T.S. / brakes (same circuit) and lights..

These are handy for trouble shooting problems:

http://www.delcity.net/store/7!way-tester/p_791230.a_1

grouch

The dealer should be able to print out a wiring schematic. The 7 pin is a standard RV plug so an RV dealer might also be able to tell you what wire it which. I had a 7 pin once that I hooked up and used for a car trailer. I hadn't noticed but when my left turn signal would flash, the brake controller was engaging. One day I turned on my left turn signal with a car on the trailer and my brakes were engaging each time the left signal flashed. I hadn't sealed the wiring harness good enough and water had run down inside the connector and rusted the screw holding the wire in place. Fluffy rust had built up and shorted out the connector inside.

If the truck lights work, I'd say the problem is in the connector. Do the brake lights work on the trailer? How about the tail lights? If you hook another truck to the trailer, do all the lights work right? I assume you've checked the pin with a volt meter or test light.

fallen1948

Yes I've checked the pin with a volt meter and there is no power going to it. All the other lights work except the left brake light. All fuses are good.

Jeff in TD

I don't recall for sure, but this year may be controlled by the integrated power module...

elirandolph

Yep that is what was wrong with mine when I didn't have a blinker and brake light on one side. I had to put a new PDC or fuse block to fix mine.

PCM

Yep, had the same thing happen to my '06. Had to take it to the dealer for a fix. They didn't charge me. No problems since. pcm

CarpUnlimited

The same dead turn signal/brake thing happened to my 04 3/4 ton on the right side. This is all that is wrong with the power mod. What I need is some technical electrical help. Since it is only one relay that is bad. Can we just figure out how to add a relay and skip the $700 replacement? If it is happening regularly, and may happen to me again, I am looking for a way around the replacement of a part that is 99% working. I have the wiring schematic. What I need is help from someone who knows about relays. What do we have to loose? All we have to do is to find a way to combine the signal from the right brake and the right turn signal without having any feedback into the system. A relay should be able to accomplish that. The wires for turn signal and brake are already back to the truck's right rear taillight assembly and they are easy to find.

Colo_River_Ram

do a search a well documented thread was done on it already or you can add a HD modulite for $65 and be done with it..

SOhappy

If all else fails install one of these before replacing the IPM:

https://www.dieseltruckresource.com/...light=modulite

CarpUnlimited

Thanks, exactly the kind of help I was looking for...a Modulite will be on my truck soon.

Brad5502

Modulite fixed the same problem in my truck. Easy instal.