Canon Rebel EOS Rebel Ti1 will not auto focus

SOURCE: Camera won't shoot with lens on Auto Focus

Talked to canon support, they suggested to send lense in for review/repair. They said it could be the motor, I think it was a gear problem based on the noises and jerkiness of the focusing action while in manual focus (manual focus gave out as well). Cost TBD - "would definately be more than $50. I shopped around and elected to buy a new lense rather than try to hassle with the repair, shipping, insurance, and the wait, etc. Besides, I have a deadline that I need the lense for, so repair at Canon really became a non-option. I think the cost would've been pretty much the same in the end as the new lense, since this wasn't one of the costlier of lenses to begin with.

SOURCE: Canon EOS Rebel

This is just a cut and paste from the user manual, but should do what your after.

SOURCE: Canon EOS Rebel problem

This is usually caused by a defective shutter release switch - it'll have to go into a repair shop - independent shops will charge about $110 USD - Canon charges about $180

SOURCE: Auto focus suddenly stopped working

This may not be the same as your issue, but our AF stopped working as well. I tried all the recommended fixes - removing the card and battery, recharging the latter, removing the lens and cleaning the contacts, etc. None of those things worked. However, I then switched to MF, requiring me to turn the barrel, and I realized it was stuck and just needed a little force to get unstuck. Might have been the humidity. Anyway, our problem was solved - AF was back to normal after that.

SOURCE: auto focus blocked Canon Eos 1000D

Try cleaning the contacts on the lens and body where they meet with a cotton swab lightly dampened with rubbing alcohol.