FRANKFURT (Reuters) - Germany's Daimler AG <DAIGn.DE> has temporarily halted deliveries of a truck engine after finding that, in certain driving conditions, its emissions of nitrogen oxide (NOx) could exceed legal limits, the company said on Sunday.
Stuttgart-based Daimler, responding to a report in the Bild am Sonntag newspaper, said it had informed Germany's Federal Motor Transport Authority of the issue last month and was in a "constructive" dialogue.
German automakers have been under intense scrutiny since the "Dieselgate" scandal of 2015, in which Volkswagen <VOWG_p.DE> admitted to using illegal software steering its diesel engines to cheat emissions tests.
Volkswagen reached a multi-billion-dollar settlement in the United States, but the scandal continues to reverberate in Germany where the head of its Audi unit, Rupert Stadler, has been arrested in a separate investigation.
Daimler is also under scrutiny over how its diesel car engines use a urea nitrate additive, called AdBlue, to neutralise emissions of nitrogen oxide, which can contribute to the formation of harmful smog and ozone.
Germany's Transport Ministry said last month that 774,000 Mercedes-Benz vehicles in Europe had been found to contain unauthorised "defeat" devices and ordered Daimler to recall 238,000 cars in Germany.
In the latest case, Bild am Sonntag reported that Daimler had found during internal checks that software running the OM 501 truck engine would, in certain circumstances, stop the injection of AdBlue.
In a statement, Daimler said the report was misleading and that the engine's on-board diagnosis system was designed to manage the flow of AdBlue in unusual circumstances such as when the engine was running on biodiesel.
This would prevent excessive injections of AdBlue leading to the release of ammonia, which in high concentrations can act as a respiratory irritant.
"In the course of regulator tests, Daimler AG found isolated situations when a six-cylinder heavy-truck engine of the Euro V standard slightly exceeded the relevant NOx limits," the company said.
Daimler said it had undertaken a detailed analysis of the findings and informed the Federal Motor Transport Authority at the end of June.
The motor was sold in Mercedes-Benz trucks in Europe until 2013, and is currently on sale only outside Europe. "Until the technical issues are clarified, the company has taken a precautionary decision no longer to deliver this engine," Daimler said.
(This version of the story corrects to read "manage the flow" not "switch off the flow" in paragraph eight.)
(Reporting by Sabine Wollrab and Douglas Busvine; Editing by Dale Hudson)
