Lil Scrappy -- RELEASED from Jail

Lil Scrappy is a free man ... for now ... after a dubious pee test led to him being thrown in the slammer, TMZ has learned.

As we reported, Scraps turned himself in to ATL authorities yesterday in response to a warrant that had been issued for his arrest. The warrant was issued over an alleged probation violation, stemming from his 2008 pot bust.

Scrappy had been ordered to submit to a urine test in March, but according to authorities, he turned in a sample that was cold to the touch and may have been tampered with. Scrappy was asked to submit another cup, and allegedly refused.

Scrappy tells TMZ, the warrant was bogus because he never submitted bad pee in the first place.