Yamaha rider Lorenzo leads Honda's Pedrosa by 23 points in the championship.
They are the only two riders who can win the crown with two races remaining.
Lorenzo has promised he won't "go crazy'' at Phillip Island this weekend in his attempts to wrap up the title ahead of fellow Spaniard Pedrosa, even though he could secure it with the right mix of results at the second-last race of the year.
"It would be great and we have possibilities (to wrap up the title at Phillip Island), but we're not going to go crazy to make it here,'' Lorenzo said.
"The most important thing is to make it.
"More than ever we must really concentrate and focus and not make any mistakes.''
Australian Kris McLaren, making his MotoGP debut as a replacement rider for the Avintia team, was slowest of the 20 riders with a 1:40.657 fastest lap.
A second practice session is scheduled for later on Friday ahead of Saturday's qualifying and Sunday's race.
- AAP