I have a 1999 chevy silverado old body style and i cant get the key fob to program or the truck into pragraming mode. Im not sure if i have the wrong key fob or which method to use?

 

What happened? Did you get a new one or just change the battery? If you just changed the battery all you have to do is stand a few feet from the truck and hold both door lock and door unlock at the same time for 7 seconds. To program a new one try link below.

How to Program a Keyless Entry for a Chevy Silverado: 9 Steps

 

it didnt come with one when i bought it used

 

One of my lock cylinoids doesn't have enough power to lock a door. Would that effect it on any way if it won't lock fully?

 

It would only cause a problem for that door.