2004 Ram 2500 4x4 Diesel. Lamp out light came on yesterday, both headlights still working.
Lamp out came on again after starting, this time passenger side low beam out. Bought bulbs on way home replaced both.
Drive to work today no problem - start truck up to go home - lamp out again passenger side low beam.
Bulbs don't appear burnt out.
Any advice - thoughts?

 

Alright.... Driving down I-35E south out of Dallas and the damn low beam comes back on lamp out light goes off..... Looks like I have some loose wire or ground to chase down.

 

Could be a lot of things. In my case on my 2004 1500 it was a bad FCM (front control module). A little silver box that attaches to the PDC (fusebox). I thought it was a loose wire because it started out sporadic but turned out to be bad FCM.

 

Good piece of knowledge - thanks. So the FCM is attached to the fuse box? Any chance you could send a post a pic if it?

 

I went through the same thing with my 1500, bad driver side tail light. driving damn the highway and heard a bang lamp out light came on got out and checked, everything worked fine until I turned the lights on later in the day. replaced the bulb and all good.

 

Sure, 4 screws hold it to side of fuse box. I got lucky and got a used fusebox that had one attached to it, ebay for 100 bucks. If you go to dealer they'd probably want at least 500 bucks for just the FCM.

 

Problem solved gents, it was the FCM. Since retiring from the Marine Corps I do a lot of motocross dirt bike & restore vintage bikes on the side and go to work as a diesel & hydraulic mechanic for heavy dirt equipment & ariel lift equipment so I have limited experience with the automotive side but can usually figure out most of it with good guidance like I find on this forum.
I looked up new FCMs they range from $350 online to $500 at the dealer. Looked at used ones and could only find (2) both priced out at $180. I got up early yesterday and rolled out to a local junkyard & luckily found the same year model Ram 2500 diesel. The engine was missing so it was easy as hell to get out. Walked up to the counter with my "used FCM" and the chubby twenty something kid was very hard at work watching YouTube videos.... I said hey what do you want for this FCM out of an 04 Dodge Truck. "Uhhhh like what would be your price dude?"
"$50"
"Uhhhh can you like maybe come up any higher man? My boss tells me to ask that like totally every time ehhh so exhausting bro"
"Sure I'll come up... $51"
"Sweet dude that's cool let me ring you up"
I give him (3) 20$ bills and see the confusion set in as he's thinking about making change....
"Uhh hey bro I only have like a $5 and some change no tens"
"Just give me the five and we'll call it even"
"Oh thanks man"
So out the door for $55 bucks & the truck is fixed, thanks guys........ Errr ahhhh like totally

 

Also one thing I noted was when the FCM is malfunctioning I still had 11.75v at both driver and passenger side head light sockets. Even the low beam that was not working had voltage. If one didn't know about the FCM or have the wiring schematic in hand this could confuse them. And like the guy above said - remove the FCM and power up the #1 pin and the passenger side low beam came back on confirming the FCM was faulty.

 

Pics for reference -

 

Thanks for the update. Congrats, you got a good deal on that one.