Toyota has ordered dealers to stop selling some versions of popular models including the new RAV4.
Technicians are inspecting the RAV4, Camry, Corolla Hatch and Prius models for potential brake defects.
The Lexus ES sedan and the UX SUV are also affected.
All vehicles are available with 1.8 or 2.5-liter four-cylinder hybrid engines, but Toyota will not say if the problem is specific to hybrids.
The cars were not recalled, but spokesman Orlando Rodriguez says they will be subjected to a "temporary stop of sales, as a precautionary measure, to ensure the consistency of production between those vehicles".
"Toyota has identified that the brake parts may require an inspection and has therefore ordered a halt to sales of selected vehicles," he said.
"Before the sale, an inspection will be carried out before delivery to avoid any inconvenience to customers."
Automotive site Motoring.com.au he first reported that the problem concerned the hybrid examples of the new RAV4 SUV.
Toyota has not confirmed whether the problem is limited to hybrid-powered cars or the number of cars affected.
In May, one in six Toyotas sold was a hybrid. About 60 percent of RAV4 and Camry sales – and 45 percent of Corollas were hybrids.
Rodriguez would not go into the question of braking.
"This is a precautionary measure only at this stage and we are in the investigation phase," he said.
"Vehicle inspections have begun and we will provide further details on the expected completion times and the consequent cancellation of this sales stop, as soon as possible."
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