A Choice magazine sting has exposed some Sydney car dealerships for not finding simple faults in customer cars. By KELLY BURKE.

Dodgy car dealer mechanics are rampant across Sydney if a sting conducted by the consumer group Choice is anything to go by.

Holden dealers fared worst of the four brands tested, nudging out Ford, Subaru and Toyota.

The trap was simple: plant four obvious faults in each of four popular cars - a Ford Laser LXi, a Holden TS Astra Classic, a Toyota Echo and a Subaru Liberty - and send them off to dealer service centres for a basic safety check and service.

Each car had a broken reverse globe, a flat spare tyre, a rear tyre with pressure 20 per cent lower than the manufacturer's recommendation and dangerously low brake fluid.

Each dealer was told the female owner was planning an interstate trip and wanted to make absolutely sure her car was safe. Yet only three out of the 28 dealerships passed the test by identifying and repairing all four faults.

Holden's website boasts that "all Holden dealers subscribe to a standard of excellence" and that all Holden vehicles "are correctly diagnosed, repaired and serviced, resulting in consistent 'right first time' performance".

But at Lansvale Holden, a $140 service failed to pick up any of the planted faults, but did manage to provide the owner with a list of $300 worth of other minor faults which were subsequently found to be unnecessary or non-existent by Choice's independent mechanic.

The dealership refused to comment yesterday and Holden's central office did not return the Herald's calls.

While another Holden dealership - Heartland Holden in Penrith - received a perfect score, collectively the seven Holden dealerships failed to correct more than half the faults planted. Stewart Toyota in Sutherland and SVM Subaru in Hornsby were the only other dealerships which identified all four faults, and overall it was the seven Toyota service centres which collectively scored the highest.

Choice's spokesman, Christopher Zinn, said the results did not surprise him as the organisation had received a significant number of complaints against dealer service centres from the public; most complainants did not have the knowledge to challenge the opinion of a mechanic.