Scott Pye will take over the driving duties of the No. 17 Ford Falcon beginning with the Tasmania race.
"I would like to make it clear that I am fully committed to this team, ” said Ambrose, who won 28 races over five seasons and captured back-to-back V8 Supercars titles in 2003 and 2004.
“Although this is a decision which has been hard to make, it has become clear to me over the first two events of the season that I need more experience in these cars to do what is required of the lead driver and to be competitive for the team and our partners."
Ambrose, who produced a top finish of 12th this season, expects to return to the cockpit this year including serving as co-driver in the 2015 Endurance Series races for the team.
"Entering the season, Marcos understood that the competition in this series is at a very high level and now realizes that more time is required for this transition," said team co-owner Roger Penske. "This was a difficult decision for Marcos but I appreciate him thinking about the greater good of the team."