Not sure what these front lights are for. Do I need them ?

[unflagging]

2002 Silverado.

 

The top row is low & high beam.
Low beam stays on while truck is running.

 

The bottom row is blinker/blinker/????
The inner 3rd light does not turn on.  
What is that called?  What it is even for, before I replace that bulb?

 

I pulled the bulb out, and it's got a square base socket.   
Is it one of these?   What's the difference of these two ?

Parking Light Bulb Size: 3157A
Daytime Running Light Bulb Size: 4114LL

 

I just looked at the old bulb.
It says 4157A on it. So, it looks like 3157A

What is the "parking light" for ?
When does it go on?

 

https://www.gmtruckclub.com/threads/bulb-sizes-for-99-02-silverados.27092/

 

 

Edited May 23, 2021 by unflagging

[CamGTP]

They are just the daytime running lights. If the light sensor on the dash worked and the headlight switch isn't on, the daytime running lights will be on.

 

 

[JimCost2014]

1 hour ago, unflagging said:

2002 Silverado.

 

The top row is low & high beam.
Low beam stays on while truck is running.

 

The bottom row is blinker/blinker/????
The inner 3rd light does not turn on.  
What is that called?  What it is even for, before I replace that bulb?

 

I pulled the bulb out, and it's got a square base socket.   
Is it one of these?   What's the difference of these two ?

Parking Light Bulb Size: 3157A
Daytime Running Light Bulb Size: 4114LL

 

I just looked at the old bulb.
It says 4157A on it. So, it looks like 3157A

What is the "parking light" for ?
When does it go on?

 

https://www.gmtruckclub.com/threads/bulb-sizes-for-99-02-silverados.27092/

 

 

If your bulbs are not burnt out, this series loves to go through them fast.

With the truck in drive, with no other lights on, it will look like this (know it is a Sub in the picture, but same lights as you have).

 

[txab]

Put the correct bulb in (4114LL). The bulb is a 14 volt bulb instead of normal 12 volt, thus it last longer than the original bulbs.

 

As noted above, will only illuminate with transmission drive, reverse, etc... Not on in Park. Should only be on during daylight. The sockets sometimes go bad due to people using the incorrect bulb or not seating it well, then generating heat causing melting Long Life bulb does last pretty well. Or go with the LED version if wish to spend more