Report: U.S. Finds Suspicious Emission Software in Mercedes Diesels

The U.S. has identified two software programs that appear to enable Daimler AG’s Mercedes-Benz diesels to exceed legal emission levels by a factor of 10, Bild am Sonntag says.

The German newspaper reports that unspecified U.S. investigators found a program called “Slipguard” that can detect when the vehicle is undergoing lab tests and another called “Bit 15” that turns off emission controls after 16 miles of on-road driving.

Both programs affect the rate at which AdBlue, a urea compound used to lower nitrogen oxide emissions, is consumed by the engine.

In tandem, the two programs could enable a diesel to perform as intended during emission tests but then ignore emission limits in real-world conditions. Switching off the emission controls lengthens the interval between when owners must replenish their vehicle’s AdBlue tank and may improve fuel economy, acceleration and/or other performance characteristics.

Bild also references emails among Mercedes engineers questioning whether the effects of the two software programs were legal.

Daimler has declined to comment, citing a confidentiality agreement with the U.S. Dept. of Justice. But the carmaker says it is cooperating fully with regulatory officials. Automotive News cites a Daimler spokesman who suggests the documents were leaked to Bild selectively “in order to harm Daimler and its 290,000 employees.”