Toyota Motor (7203.T) said it would suspend shipments of some models including the Hilux truck and Land Cruiser 300 SUV after finding irregularities in certification tests for diesel engines developed by affiliate Toyota Industries (6201.T).
A special investigative committee found irregularities during horsepower output testing for the certification of three diesel engine models.
Ten models use the affected engines globally, Toyota said, including the Hiace van, Fortuner SUV, Innova multi-purpose vehicle and Lexus-branded LX500D SUV.
Toyota, the world's biggest automaker by sales, has been separately seeking to resolve a case of misconduct related to rigged collision safety tests at small car specialist Daihatsu.
The company said it sought to thoroughly explain the matter to authorities and would take measures such as running new engine certification tests in the presence of regulators as needed.
"There was a lack of communication with Toyota Motor and not enough coordination about testing processes and procedures that should have been followed," Toyota Industries President Koichi Ito said at a press conference.
Toyota Industries said it sold about 84,000 affected automobile diesel engines during the financial year to Mar. 31, 2023. A Toyota spokesperson could not immediately say how many affected vehicles the automaker had sold over the years.
The company said it had re-confirmed that affected engines and vehicles met engine performance output standards.
It added the investigation had found that electronic control units used during horsepower output testing were different from those used during engine production.
Japan's transport ministry said it would on Tuesday conduct an on-site investigation of Toyota Industries' Hekinan plant in central Aichi prefecture where the company makes automotive and industrial engines.
Toyota's investigation initially focused on certification regulations relating to emissions performance of forklift and construction machinery engines, in which the special investigative committee also confirmed misdoing.
The company holds a near 25% stake in Toyota Industries, which is a key Toyota group company. The supplier in turn owns about 8% of Toyota shares itself.
Shares in Toyota Industries sank into negative territory shortly after the news and ended down 4%. Toyota Motor shares closed 3.1% higher.
