FRANKFURT -- Daimler 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.
Daimler, responding to a report in the Bild am Sonntag newspaper, said it had informed Germany's Federal Motor Transport Authority (KBA) of the issue last month and was in a "constructive" dialogue.
German automakers have been under intense scrutiny since the Volkswagen Group in 2015 admitted to using illegal software to cheat emissions tests.
VW Group reached a multi-billion-dollar settlement in the U.S., 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 neutralize 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 unauthorized so-called "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 switch off 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 found isolated situations when a six-cylinder heavy-truck engine of the Euro 5 standard slightly exceeded the relevant NOx limits," the company said.
Daimler said it had undertaken a detailed analysis of the findings and informed the KBA at the end of June.
The engine was sold in Mercedes-Benz trucks in Europe until 2013. It 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.
