My dually is sending the left brake/signal to the trailer harness. So the left brake light is on as soon as I plug in any trailer. I checked the harness all the way to the fuse box and can't find anything. The wiring diagram shows a relay after the fuse #46 but I can't locate it for the life of me.

Does this happen with the key on only or off to . And if you ck for power on the turn/brake terminal at the plug. There a diagram on the cover if it's a factory plug w/ key off should only be power at battery

Probably just another bad TIPM, it will only cost you $600 or so to fix it if you can find one. I played hell trying to fix my trailer running lights and turn signals as the TIPM was giving me fits from around 2006 until I sold the truck...

quick youtube search found this

link

Thanks guys! Yes the left brake light on the trailer only is on all the time. Yes the left turn/brake pin is constantly hot. The fix doesn't look so hard from the video. My next question is, would a failed relay keep something constantly hot? Seems to me it would be the other way and not send any signal? Thoughts?

Well, I suppose a relay could somehow stick then fail, but that seems far fetched.

I definitely would open up that TIPM and get a meter on the contacts to see whats going on

My bet is the relays rating is to low. The contacts over heated and fused together.
Doug

You can repair it all you want, but this is just the start of things to come, DAMHIK! Do a lot of research on the TIPM, what a piece of junk!

Ok. Sorry for your troubles Rhino. I'm guessing the TIPM is the fuse/relay center box. This thing has been solid for 300,000 miles. ROCK solid! I wouldn't call it junk. If a $600 bill gets me another 300,000 it seems pretty fair to me. I have to agree that for vehicles that were built to tow this is pretty dumb. If you have a relay, why wouldn't it be plugged in to the top with the rest of them? I blame it on the Germans. For now I'm heading to Vegas with my left brake light on. I just turn the rest of the lights on so it's not so obvious. The left signal still blinks a funny little blink. Thanks for the help guys!

Well mine started giving me problems with 40K miles on it, probably because I live in a State the salts the heck out of the roads. I lived with it until the engine blew at 165K miles and I decided to try and fix it while the engine was out. By then you couldn't buy a new TIPM because everyone else had already had problems with theirs and Chrysler was sold out so I had to get a used one. After the second used unit I finally had all my lights working, then my trans problems kept coming on and I sold the truck at a loss.

The TIPM is more than just a relay/fuse center. It has an internal module that controls body control functions. 3 possibilitys. A: the trailer stop/ts circuit is shorted to a a hot circuit. B: the internal relay is stuck. C: the module control for the left turn signal is commanding the relay on. The #3 possibility is unlikely if the truck turn signal/brake lamp function normally with the trailer disconnected. You could always tap into the tail lamp circuits as wel. This would require a splitter (U-haul is a good source) as your truck has seperate TS and brake lamp circuits.
Doug

Thanks Doug! I knew some good techs would chime in! I have traced the wire all the way back to the TIPM and I can't find anything shorted. The truck functions normally so I have to go with the "B" door. Great idea on the tapping into the tail lamp on that side! Just cap off that yellow wire and run a new one from the tail light! Probably easier than what the guy in the video did. Do you see any potential problems with doing it this way? ie; needing a higher amp fuse or relay on that side?

The only issue is without a splitter box you will not have a brake lamp on that side (or turn signal). The trailer is one circuit, the truck has separate circuits. Disasembly of the TIPM isn't that bad.
Doug

If you need a TIPM for parts I still have my original.

Damn I hate to tear into this thing. I use my pickup all the time. I'm heading to Vegas next week so I won't be doing anything soon. Thanks again!