Hino Motors said Friday that it has uncovered years of falsified engine data believed to affect as many as about 115,000 vehicles -- double the Toyota Motor subsidiary's annual sales in Japan,
As a result of the investigation, Hino has halted shipments of medium- to heavy-duty trucks and buses with three types of engines linked to the data manipulation.
The revelation is the latest to call into question data on emissions and fuel economy in the automotive industry, which has seen Volkswagen, Mitsubishi Motors and others own up to cheating.
"There was a failure to handle the pressure to reach numerical targets and to strictly adhere to schedules," Hino President Satoshi Ogiso told reporters Friday.
The misconduct occurred at Japanese facilities where Hino conducted engine tests. In one of the engines, an exhaust system part was replaced during testing until the desired results were achieved.
Hino decided to launch an internal investigation into possible irregularities after discovering in 2018 that vehicles bound for the North American market had engines not in compliance with U.S. regulations.
The company later widened the probe to include engines for the Japanese market, upon which the misconduct came to light.
The data-rigging dates back to at least around 2016. That year, when Mitsubishi Motors was rocked by a fuel economy data scandal, Hino told a transport ministry probe that it had found no data manipulation.
"Not discovering the misconduct is a huge problem for our company," Ogiso said Friday.
Because retesting will likely generate emissions levels exceeding legal limits, an estimated 43,000 trucks will be subject to a recall.
Hino's engines are found in buses made by parent Toyota and by Isuzu Motors. The revelations apparently affect 3,000 Toyota buses and 1,200 Isuzu buses.
"Hino must first take responsibility by getting to the bottom of the situation as soon as possible and by taking full preventive measures," a Toyota representative said. Toyota will support Hino's efforts toward this end, the source said.
Hino, which operates independently of Toyota, sold 59,676 trucks and buses in Japan during the fiscal year ended March 2021. It holds a 30%-plus share in commercial-vehicle sales.
This latest development adds to Hino's troubles. The automaker said in 2020 that it would suspend operations at two North American truck plants over delays in obtaining U.S. certifications for engines.
In December, Hino recalled about 47,000 Profia heavy-duty trucks. Pipes were improperly fitted in a way that released nitrogen oxides above regulatory limits.
Neither episode is linked to the data manipulation, according to Hino.
The Ministry of Land, Infrastructure, Transport and Tourism on Friday ordered Hino to conduct a thorough investigation into the matter and to explore preventive measures. The ministry also ordered seven makers of heavy-duty trucks to launch probes, including Toyota, Isuzu and UD Trucks.
The companies are given a deadline of April 8 to report any irregularities.
Hino's data-rigging "erodes the trust of automobile customers and shakes the very foundations of the certification system," the ministry said in a news release.