The driver, aged 37, was found lying unconscious on Nullabor Street at North Kellyville, near Sandbanks Avenue, by officers who responded to reports of a brawl in the street.
The man suffered injuries to his head and paramedics were called who treated him at the scene.
He was later taken to Westmead Hospital where his condition was stabilised.
Later this morning, police arrested a 19-year-old man close to the scene and took him to Castle Hill Police Station.
The man from North Kellyville is alleged to have been one of three passengers in the vehicle.
Two other passengers – an 18-year-old woman and a 22-year-old man – are also assisting police with their enquiries.
Officers found a wrench at the scene which has been taken in for forensic examination along with a Toyota Camry sedan.
Anyone with information on the incident are urged to contact police or Crime Stoppers.