Strange behavior of factory LED brake/turn signals

[rikbakke]

This is a teaser - My cousin has a 2014 1500 RAM Express (purchased used) with factory turn/brake LED lights - same as Laramie - these are factory installed as part of an option package, not aftermarket.
The LH tail light works fine with the ignition switch in 'on' position and the engine is not running - brake good, LH turn good. All lights work fine.
With the engine running, the LH tail light brake/turn LED array is on constantly - bright lighting for brake and turn, not running light intensity. The front turn LH turn signal works fine as does the RH light. running lights work fine on other three corners. as does the reverse/backup lighting.

Is it a light problem? is the light module powernet 'intelligent'? there's quite a few wires going into the light so I think not so much?
Wiring issue?

Full disclosure: I pulled the tail light out and found a old pigtail scotchlok'ed to the backup lamp wiring. someone spliced into it it seems to pull 12v for an extra lamp - no sign of the extra lighting today. the spliced wire is a 2 conductor wire that was snipped cleanly - the conductor ends were not wrapped and may have shorted with corrosion or contact with the box.

Strange it works with engine off, and not with engine running.

Glad my 2500 tradesman has incandescent lighting...

Anyone have similar issue? Solution?

Thanks!

Erik B.

 

[Bob4x4]

I am going to guess there will be a dtc set that will give you a good direction to go on your diag.It will require a scanner capable of seeing the bcm

 

[PTsideshow]

the rams/Dodges are famous for the multi-function switches going bad the one in my 98 went and it was a pain to find out what was wrong, as a side note wife was a CAD designer that worked on the Wiring harnesses when she asked the engineer that designed it if he knew what could be wrong he told her his was screwed up too and if I figured it out to let him know. Dealer wanted over $1,000 to trouble shoot the problem. I bought a 2016 2500 and the multi function switch was acting up, wipers, lighting and turn signals. Had to take it bake the second day I owned it. now the switch is also tied into the software. so it could be just an update for bugs if it has that type.

 

[Bob4x4]

the rams/Dodges are famous for the multi-function switches going bad the one in my 98 went and it was a pain to find out what was wrong, as a side note wife was a CAD designer that worked on the Wiring harnesses when she asked the engineer that designed it if he knew what could be wrong he told her his was screwed up too and if I figured it out to let him know. Dealer wanted over $1,000 to trouble shoot the problem. I bought a 2016 2500 and the multi function switch was acting up, wipers, lighting and turn signals. Had to take it bake the second day I owned it. now the switch is also tied into the software. so it could be just an update for bugs if it has that type.

I have not had to replace a single m/f switch on a 4th gen truck,and I work on them daily

 

[Road Dog]

You could start with a reboot -- disconnect the batteries (or pull the main fuse), wait, and power up. All the computers will go through a self retest and reset.

 

[Dodger2014]

Mine acted up the other day.... Not same scenario as yours but I did disconnect the batteries for a half hour. It made a difference! Before I used the tow/haul mode and I could tell the different shift points but now when you touch the brakes it will downshift as you are slowing down. Maybe placebo effect or wishful thinking but it seems to run better.

 

[rikbakke]

Thanks for the helpful suggestions. We'll try the battery disconnect in the morning.
Further investigation shows 1), the bright brake/turn LED output is only when the parking/running lights are on. When parking/running lights are off, the LH LED array is on but very dim.

 

[Road Dog]

That would indicate a missing ground. I have no idea if the 2014 is positive switched (lamp is always grounded) or negative switched (lamp always has +12v). .

 

[rikbakke]

Issue resolved. Road Dog you rock.
A screw used for a large aftermarket mud flap attach penetrated the wiring harness.
A little soldering and harness cleanup - and a proper fastener - fixed it.
Thanks again for all the suggestions.

 

[Road Dog]

Or an extra ground in this case. Glad I could help.

Trailers are notorious for this kind of problem since every lamp housing uses a screw to the frame for the ground.