Timani appeared before International Rugby Board Judicial Officer David Martin on Wednesday having been cited for striking an opponent in the 13th minute of Australia's narrow 22-19 victory in Florence.
"Acknowledging the player's admission of having carried out the act of foul play, the Judicial Officer deemed the incident to be at the low end of the IRB's table of offending and suspended the player for one week, having taken into account the mitigating factors," a statement said.
Timani's absence leaves Australia coach Robbie Deans lacking forward options for Saturday's match.
Nathan Sharpe and Cadeyrn Neville are the only two available locks in the squad.
The eight-week ban handed to Australia's Rob Simmons for a tip tackle on French flanker Yannick Nyanga has been reduced to five weeks but the lock will still miss Saturday's Test.
Simmons, on as a replacement at the Stade de France, was cited for a tip tackle on Nyanga in the second half of the match won 33-6 by France earlier this month.
The reduced punishment rules Simmons out of the Wallabies' last match on their tour of Europe against Wales after he missed the matches against Italy and England.
The Six Nations Committee said in a statement that the player will be free to play from February 4.
"The appeal committee ... found that the player's offending had merited a mid-range entry point, rather than the top end entry point that the Judicial Officer had originally found," they said.
"After applying aggravating and mitigating factors, the appeal committee imposed a reduced sanction of five weeks."
The Wallabies will travel to Cardiff looking to make it three straight Test wins after victories over Italy and England following the defeat by France.
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- Rob Simmons