GM faces suit for alleged VW-type diesel emissions scam

General Motors is facing a lawsuit over alleged programming of some of its heavy-duty pickup trucks to cheat on diesel emission tests in a manner that immediately brings the Volkswagen emissions scam to mind.

The class-action suit has been filed by a Seattle law firm that specialises in suing automakers – the same one that had targeted the Volkswagen Group in the US. With this, GM becomes the fifth automaker to be accused of diesel emissions cheating since Volkswagen AG admitted doing it in 2015.

News of the lawsuit sent the company's shares down almost 2 per cent on Thursday. It is the latest sign that the methods that automakers have devised to meet stringent diesel-emissions regulations is under intense scrutiny. The issue has led to major legal cases against Volkswagen and Fiat Chrysler.

The class-action suit filed on Thursday in Detroit federal court covers a total of 705,000 trucks equipped with Duramax diesel engines

General Motors denied the allegations. ''These claims are baseless and we will vigorously defend ourselves,'' it said in a statement.

It was unclear whether environmental regulators would open investigations into GM and the emissions-control technology used in its diesel trucks.

The suit accuses the company of using software that helps the diesel versions of Chevrolet Silverado 2500HD and GMC Sierra 2500HD heavy-duty pickup trucks with Duramax engines meet emissions requirements.

The software was used in trucks sold from 2011 to 2016, the suit says. It argues GM deceived customers by marketing the vehicles as ''clean'' diesel trucks and seeks to force the company to buy the vehicles back and compensate owners for economic losses.

Bosch co-accused
German auto supplier Bosch also is named as a defendant in the lawsuit which portrays the companies as ''an acting and knowing participant in the scheme to evade US emissions requirements.''

Both companies are accused of programming software ''to detect a possible emission testing environment and to comply with emissions requirements in that circumstance, but to turn off the emissions controls when ... testing ... is not detected.''

According to the suit, the trucks conform to emissions standards when they are being driven at steady speeds and when outdoor temperatures range from 68 to 86 degrees - the conditions used for some of the emissions testing such trucks undergo.

In the absence of those conditions, the vehicles emit four to five times the pollutants than are allowed, the lawsuit says. It alleges that GM intentionally programmed the vehicles' emissions controls to pass emissions tests and to then scale back those controls in real driving conditions to improve power and fuel-economy.

In response to the suit, GM said heavy-duty trucks with its Duramax diesel engine complied with all emissions regulations of the Environmental Protection Agency and the California Air Resources Board, which plays an influential role in vehicle emissions.

The suit was filed by Hagens Berman Sobol Shapiro, a law firm that specialises in class actions and that previously filed a diesel-emissions suit against GM related to the Chevrolet Cruze compact and another against Fiat Chrysler; those suits are pending. A similar suit filed by the firm against Mercedes-Benz was dismissed. Hagens Berman has also filed liability claims unrelated to emissions against Ford Motor, Kia Motors, Tesla and others.

Hagens Berman said the suit was based on tests it conducted on a 2013 Silverado 2500HD with about 51,000 miles on the odometer. Steve W Berman, a partner, said the firm had hired its own engineers to test diesel vehicles after Volkswagen acknowledged in 2015 that it had cheated on emissions tests.

''We came to the conclusion that all manufacturers in Europe had cheated, and we began to ask, 'How could it be that the vehicles manufacturers are selling in the U.S. are clean?''' Berman said.

The diesel versions of the heavy-duty Silverado and Sierra make up a small portion of GM's total United States sales, but contribute significantly to its bottom line.

'Clean' diesel?
A decade ago, BMW, Mercedes and Volkswagen began offering a new generation of cars that they promoted as ''clean diesel.'' They were designed with new pollution-control technologies and intended to meet more stringent emissions limits being set by the European Union and California.

Among the innovations was a system that sprays ammonia into a vehicle's exhaust system to remove nitric oxide, one of the most harmful pollutants in diesel exhaust. New filters that trapped and burned particles common in diesel fumes were also introduced.

But then Volkswagen began selling cars that passed the tighter emissions tests without using the exhaust additive, which is known as urea. Researchers at West Virginia University and elsewhere eventually discovered that emissions from VW's diesel models were far higher on real roads than in tests, and the Environment Protection Agency demanded that the company explain the discrepancy.

In September 2015, Volkswagen admitted that its cars had used software to detect when they were being tested, and to turn on emission controls. In real driving, the controls were dialled back to give cars better fuel economy and a peppier ride.

In all, Volkswagen sold some 11 million cars and sport-utility vehicles - including about 600,000 in the United States - equipped with the offending software.

In Europe, where diesel cars account for a much larger portion of the market, regulators and researchers have begun investigations of several automakers to determine whether they are using illegal means to comply with diesel-exhaust rules.