Left side brake light not working

Hi everyone, just replaced my left side brake light with a dual filament bulb. The tail light /running light works but goes dark when the brake is depressed. The right side brake light works fine so I assume it’s not the brake light switch. Any ideas? Could it be a corroded housing or wire somewhere or is this a simple fuse I’m not seeing? Thanks for your help!

 

Welcome to the forum.

What year is your truck?

It isn't a fuse if the other side is working.
I'm going to guess you have the wrong bulb or the socket is bad.
Some Tundras have a bulb ending in a different suffix - should be a 3157KX
The leads are positioned differently than a regular 3157 bulb.
That could be why your bulb is working erratically.

 

Bulb chart for a 2019