The left rear brake bulb is out when I hit the brake pedal but it flashes when I use my keychain to unlock the car. What gives? Expensive electrical issue or simple loose connector? Thanks.

 

It's a 2057 dual-filament bulb - one filament is used for the brake lamp, and the other filament is used for the parking lamp.

It's pretty common to only have one bad filament in a dual-filament bulb.

A bulb costs $1 and takes less than 5 minutes to replace. You're thinking way too far into this instead of approaching it with the simplest solution first.

 

I didn't see much point in changing the bulb if it still lit in one condition. I wasn't aware of the dual-filament, hence why I posted here. Thanks for your very helpful albeit kurt response.