Is Dealer Blowing Smoke Up My....?

[Doubeleive]

What year make and Model - Did I miss this? I've replaced by 2011 suburban ltz lights with led and had no problem.

2011 is a different generation and not even like the k2's in any way. the k2 have at least 4-5 different configuration of lights "some" with a internal pcb board, my 18 has a board, the wifes 16 does not.
some of the lights are pretty complicated and upgrades may require bcm programming
some are not a regular pigtail to a high beam. low, blinker, etc instead it's a high density plug to a internal board that then splits the signal to different parts, led, hid, etc
and of course the housing is sealed so you can't just open it up to replace part, maybe in a oven like some mods are done but nothing simple.

 

[AJMBLAZER]

Do you still have your old housings? If so, plug one of them in and see if it works or not. It doesn't have to be the one that was cracked/corroded and didn't work, plug the good one in and see if the "control modual" recognizes it

This. I had to replace a tail light on my Silverado last year and went with an Amazon special. Fitment and appearance was perfect but I could NOT get it to flash right. Kept getting fast blinkers like if you put LED lights in place of halogen turn signals.

I ended up taking the GM harness off the broken housing and putting it on the aftermarket one. Whatever was wrong with the Amazon harness it would not work correctly.

 

[Tonyv__]

This. I had to replace a tail light on my Silverado last year and went with an Amazon special. Fitment and appearance was perfect but I could NOT get it to flash right. Kept getting fast blinkers like if you put LED lights in place of halogen turn signals.

I ended up taking the GM harness off the broken housing and putting it on the aftermarket one. Whatever was wrong with the Amazon harness it would not work correctly.

My Amazon special rear tail light works perfect . But I’m disappointed that the red led isn’t identical to the oem one. I’m procrastinating on sending my OEM one out to get fixed