Just found this code in a Jetstar flight itinerary.
The ad banner said "book and park before 31/08/2017", while I found the code still works at the moment.
I've just booked one for 5 days in October for only $36 (regular online price $45)!
-Arrive Wed 25 October 2017 09:00
-Depart Mon 30 October 2017 00:00
-Price $36.00 (You saved $43.00*)
Hope it helps.
This code works on ALL car parks including T1 T2 T3 T4 & long term.
Tried several times using different time periods.
Looks like the code can only be used if entry before 01/12/2017, while no restriction for the exit date.
Update 3 (16/10):
Only works at T4 now.