Ford driver Chaz Mostert, who was a couple of cars ahead of Coulthard, made a dive at David Reynolds at the hairpin and banged into the Erebus Racing Holden. As he fought to regather himself he grabbed the wrong gear and it resulted in a number of cars fighting for position. Coulthard tangled with Reynolds and both ended up off the track - the Kiwi on his roof.
"Me being a racer, I saw two easy passing opportunities and I went for it and we were 90 percent there," Coulthard explained. "I got a tag from Dave behind the right rear wheel, which sent me to the grass and I was a passenger from there."
It is a major blow to his championship hopes. From 17 points off the lead heading into the weekend, Coulthard now finds himself 137 points behind Jamie Whincup.
"It is not over," he said of his title hopes. "We have today if we can get it fixed and then we have got Newcastle. We will remain focused, concentrate and see what happens."