Toyota Motor is temporarily halting global deliveries of 10 vehicle models due to irregularities in engine performance tests.
Investigations revealed that the tests for the certification of three diesel engine models used in the vehicles were faulty, Toyota said on Monday.
The engines were developed by the affiliate firm Toyota Industries Corporation (TICO). They are used in 10 affected models worldwide, such as the Hilux pick-up and the Land Cruiser 300 SUV.
Toyota said the software used by TICO to measure horsepower performance made "values appear smoother with less variation."
The Japanese company did not say how many vehicles were affected.
Toyota assured that the vehicles already sold still meet "engine performance output standards" and that there was no reason for customers to stop using them.
"Going forward, we will provide detailed explanations to the authorities and promptly proceed with appropriate measures, including conducting testing in the presence of witnesses if appropriate," a Toyota statement said.
Last month, Toyota subsidiary Daihatsu halted deliveries of all vehicle models following safety defects.
