[guyonearth]

Thats incorrect, if the ground is bad with a dual filament bulb it can get enough ground to run the lower current tail light filament by grounding through the larger filament (brake t/s) by feeding from the other light.
He needs to verify which one is actually the ground and trace it to where it is supposed to be grounded. Remove the bulb and inspect the socket for corrosion. Check connections on the BCM and down line. Do all this without the new led unit because the lower current draw from that unit may cause the BCM to not recognize it. Solve in standard configuration so additional conditions are not created.

Don't you actually read posts? This is an LED module. There is no "filament". There are 6 wire positions.
RIGHT REAR LAMP ASSEMBLY - BLACK 6 WAY

CAV​	CIRCUIT​	FUNCTION​
1​	L62 18WT/BR (EXCEPT EXPORT)	RIGHT REAR TURN SIGNAL DRIVER
1​	Z362 18BK/BR (EXPORT)	GROUND
2​	L62 18WT/BR (EXPORT)	RIGHT REAR TURN SIGNAL DRIVER
3​	L50 18WT/TN (DIESEL)	PRIMARY BRAKE SWITCH SIGNAL
3​	L78 18WT/OR (EXCEPT EXPORT/EXCEPT TRAILER TOW)	FUSED PARK LAMP RELAY OUTPUT (RIGHT)
3​	L50 18WT/TN (GAS EXPORT)	BRAKE LAMP SWITCH OUTPUT
3​	L78 18WT/TN (TRAILER TOW)	FUSED PARK LAMP RELAY OUTPUT (RIGHT)
4​	L1 18WT/LG (EXCEPT TRAILER TOW)	BACK-UP LAMP FEED
4​	L1 18 WT/PK (TRAILER TOW)	BACK-UP LAMP FEED
5​	Z362 18BK/BR (EXCEPT EXPORT/EXCEPT TRAILER TOW)	GROUND
5​	L38 20WT/YL (EXPORT)	REAR FOG LAMP SWITCH OUTPUT
5​	Z362 18BR/OR (TRAILER TOW)	GROUND
6​	L78 18WT/OR (EXPORT)	FUSED PARK LAMP RELAY OUTPUT (RIGHT)

 

[aircommuter]

I read the posts, it made think the original unit was not LED and he was adding one.

 

[2012RAM1500RT]

I am the one that suggested not cutting any wires, that's always my last resort (asking for possible future problems). Getting upset at people trying to help you just shows the world we live in today. They're just trying to give you ideas. As for me I've been a mechanic for 40 years and have done very well at it. It's very hard trying to trouble shoot something when you're not there so you do the best you can. I have had 100's if not 1000's of tail lights to work properly until you turn a turn signal or brake light on and make it not work. Most of the time the park light will start flashing dimly. 90% of the time (for me) it's been a grounding issue. I'm not guaranteeing that is the problem but I am only saying that's what I would work with. I'm not looking for a cookie or a pat on the back, was just trying to help and give an opinion. You have made me reluctant to try to help others but if you don't have patience or willing to try things please take it to a dealer or shop. People on here don't charge you anything but a shop will and it may be worth the money to keep you from being frustrated. Once again I'm sorry I was unable to help you.