on one of my scion tc's tires, I have to at least put air into it at least...

[vAFLIP]

...every 2-3weeks...? could there be a tiny whole in my tires?

[Rikounet]

Likely a roofing nail or something.

[sd_waterman]

make sure you put designated scion tc air into it.

[lickablepiercing]

Bring your scion to a tire shop, goodyear, firestone, etc. that will patch or vulcanize the tire from the inside. They should also dunk the tire to check for "Small holes or leaks". or it could be a small bend in the rim itself, which can be repaired very inexpensively and easily.