SOhappy

I've documented my issues on DTR with my right turn/stop circuit going bad. I traced it down to the FCM, not the relays in the IPM like most of you (although the Modulite will fix that as well).

Not wanting to spend $300-$400 for a new FCM, I followed the advice of a DTR member and bought a Modulite HD for less than $40 on ebay. The installation was pretty easy, took less than 2 hours. I just wanted to show everybody how I mounted it in case someone else decides to go this route.

Just follow the instructions that come with the Modulite. Basically you run a power circuit down from the battery. The fuse for it can easily be mounted on the firewall. A separate kit for this power circuit can be purchased for around $10, I bought it with the Modulite so I saved a bit on shipping. Next you install the Modulite in the rear of the vehicle. I found a nice little pocket under the left-rear taillight assembly in the back of the fender:



The Modulite is adhesive-backed so it should stay put and not bounce around in there (shown in lower-center of picture).

I spliced into the signals going to the left tail light assembly , then ran a single wire over to the right taillight assembly for right turn/stop . The Modulite supposedly doesn't draw enough current to screw up your trucks computer, it doesn't throw "Lamp Out" messages on the instrument cluster.

Next you ground the Modulite ground wire to the frame. Finally you cut off the 4-pin connector on the Modulite output and splice the wires into your trailer towing harness. Black w/orange goes to brown. Yellow w/pink goes to yellow and Wite w/pink goes to green (see pict). Leave your trailer brakes, accessory wire, ground wire, etc. alone.



I put everything in plastic looms or wrapped it up with electrical tape for protection from the elements. Everything checks out with the test light, will do my first tow with it this weekend.

In principal I hate hacking my electrical system, but $40 sure sounds better than $400. I'll probably pull the trailer tow fuses in the IPM and make a sticker or something to go in there for the next owner of the truck, informing them of the changes I made.

wiskeyVI

Nice Job!!!

5.9x2

I have a question, I am new to this site and the Third gen trucks What is the IPM or for that matter the FCM this is the second time I have seen that mentioned as an expensive problem.

Joe

SOhappy

Sorry,

IPM = "Integrated Power Module" or "fuse box" for the rest of us. Besides fuses, it has relays. Some accessible (replaceable) and some not, as part of the IPM is sealed . It's actually called the Power Distribution Center (PDC). Technically, the PDC becomes the IPM when the FCM is attached to its side.

FCM= "Forward Control Module" or computer. It's attached to the side of the IPM, just a circuit board in a sealed aluminum can.

They are both expensive (at least I think so), but really the only thing that appears to be a problem is with the towing circuits. Hook up to a trailer with bad wiring and you risk blowing a circuit in the FCM (this is what happened to mine) or a sealed relay in the IPM (this is what happens to most others). Truck still runs fine and everything, you just don't have all or some of your trailer lights. The ModuleLite bypasses this problem.

BTW, towed with it for the first time over the weekend. Worked perfectly.

Rednax

Had one of these on a JEEP Cherokee. You might also test the trailer lights voltage with another vehicle (non-Modulite) and then with yours. I found that the item gave me some fast, bright trailer signalling as a result of clean power bypassing the TV electrical system. Little things add up.

Colo~Dirtbikers

I haul rv's for a living and have used one of these since I started..

I love it.. Best thing you can add to your truck if you tow much..

Why cant the factory just put something like this on instead of there junk? Baffles me!

Carey

5.9x2

50 cents is 50 cents to the Chrysler Bean Counters

Except in the long run it has cost them, I know of people that will run a Duramax or a Power Choke rather than take a risk on the Chrysler Wiring.

On my 94 I received a notice like a recall notice for the wiring, it stated that you needed to ad a Trailer circuit (they would give you a schematic) if you pulled a trailer with more than just tail lights on it as the factory wiring was not capable and that it would not be covered under warranty

Anyway this sounds like a good prevention that I will have to look into for my 04.5

One last question, what do we have to do to put Trailer brakes (controller) on our trucks if they were NOT ordered with the tow package? I see that the plug is under the dash but no wiring at the rear or a plug in to break at the tail lights for that matter (another .50 cents saved)

Thanx

ctd4stan

SOhappy,
Great write up and pictures I also have an '03 SO, but 2WD. My truck has the factory tow package, but the trailer right blinker is not working. I found out when I tried to rent a trailer from U-haul. They had a tester to fit both the 7pin and 4pin plugs and found that I had no current going to the plug. The multi-meter showed 12v at the fuse. So, it appears to be related to the factory harness and/or where the split off to the tail lights occur.

I'm not familiar with the tow light wiring (aside from #46/47 fuses), but did you install the Modulite into the factory tow package wiring?
Hence, the factory round 7pin and flat 4pin plugs worked as normal.

I'll buy the module + that $10 circuit kit. And I'm pretty sure I can follow the directions.

Brad5502

Great tutorial SOhappy. Did the install this afternoon and you had everything "wired" to a T, even the color coding. Slapped some dielectric on my trailer connector too. Will see if this fixes the problems I've been having with turn signals/brake lites next weekend when I take the 5er out. The signal output to the trailer looks real strong.

MX429

It seems to me that if the trailer plug functions good now. (no problems), then this thing should be super easy to wire in at that point and not cause you to dig into the turn signal wires themselves.

RTillery

Subscribing:

MX429

Installed mine. I wired it in at the trailer plug wiring harness. Mine worked fine. With the module installed, I shoul never have problems with it.

RFR2212

Here is my question:
Why is a Modulite worth $40? My passenger side trailer light doesn't flash or brake but works fine as a marker light. I attribute this to my IPM. So, why not run a simple 4 plug relay? My trailer is LED lit and would suspect the opening and closing of that relay would be a very minimal draw. I do not need the other channels and like that I'm only spending 5 bucks on a standard auto parts relay.

Thanks

SOhappy

That might work where your trailer lights are LED. Try it and tell us how it turns out.

Of course, you'll have to do it for every circuit that fails. At some point the Modulite (which covers all the trailer light circuits) will be worth the $40 and one-time 2 hour installation. Just my opinion.

RFR2212

Possibly. As of now, I only have 1 circuit that is bad. So, we'll give this a shot. Either way, I'll at least have the power, ground and one of the lights done already.