Greenham went into the final round of the series with just a one-point lead over rival Will White, but the championship battle was short-lived.
White crashed his Mitsubishi Lancer EVO IX MR in the first stage, putting him out of action for the rest of the night.
Knowing that he needed to post some fast times to finish ahead of Greenham, the Dardanup businessman was using the full capacity of his 2.3-litre stroker engine.
Coming into the first corner into the keyhole, he missed his braking point and ran into one of the three concrete barriers, but while he was able to minimise the damage, it was still bad enough to put him out of contention for the 2014 championship.
Get in front of tomorrow's news for FREE
Journalism for the curious Australian across politics, business, culture and opinion.
READ NOWGreenham, who has been the driver to beat for the past two seasons, went on to win the heat and retain his crown.
With either his brother Andrew or sister Sarah in the co-|driver’s, seat he finished the five-race series with two wins and three seconds to finish with a score of 47 out of a possible 50.
Greenham said the competition was a lot tougher this year.