When is a car cled as abandoned?

We are having heaps of troubles with Holden who turned our 2000 Jackaroo worth $15,000 into a car worth negative dollars (reapir costs outstrip what it is worth). We want to leave the car there so that they have to deal with it and remind them that there is a problem. We are going overseas for 6 months. Can we leave the car there for that time? Will they have any right to cl it as abandoned and sell / scrap it?