Almost three-quarters of vehicles checked in roadside inspections in the Island last winter were found to have defects.
The main problem area was lighting but inspectors say they also uncovered an alarmingly wide use of temporary fuel tank caps.
Owners are being urged to ensure their vehicles are road-worthy, in the absence of compulsory annual MOTs.
Department of Infrastructure, the roads policing unit and neighbourhood officers.
Only 123 had no defects at all, of the others the vast majority were to do with faulty lighting.
There were 63 cases of worn tyres, while damaged wiper blades, broken mirrors and blowing exhausts were among other problems.
Chief examiner Mark Pattison says he's alarmed at the use of temporary fuel filler caps for more than short periods.
He warns they can be responsible for fuel spills on the roads, endangering other motorists and creating a fire hazard.
Member for Highways Leonard Singer said it was disappointing that some owners are not maintaining their vehicles properly.
Motorists are reminded that although there's no official requirement for a periodic check, they can be prosecuted if their vehicles have serious defects.