EPA to Test Other Diesels

In a conference call to reporters this morning, EPA officials said they plan to spot-check other light-duty diesel vehicles for compliance with the Clean Air Act. The agency is notifying "all automakers that we are stepping up" oversight, said Janet McCabe, acting assistant administrator for the EPA's Office of Air and Radiation.

Related: More VW Diesel Recall News

In the past, the agency has focused its emissions testing on nitrogen oxide on heavy-duty trucks at highway speeds, whose emissions "dwarf" light-duty vehicles, EPA officials said. Nitrogen oxide is the component in Volkswagen's diesel engines that the automaker allegedly evaded emissions testing on.

It comes as all diesel automakers in the U.S. have told Cars.com that they don't use "defeat device" software that cuts emissions only during testing, as VW has allegedly done.

"Today we're putting vehicle manufacturers on notice that our testing is now going to include additional evaluations and tests designed to look for 'defeat devices,' " said Chris Grundler, director of the EPA's Office of Transportation and Air Quality. The agency isn't going to tell automakers what the additional tests are, Grundler said. It's "actively recruiting light-duty diesel" vehicles for testing.

EPA, the California Air Resources Board and Canadian environmental officials are starting the testing now. Regulators plan to test all light-duty diesel vehicles on the market, Grundler told reporters, including models "already on the road."

"We are dividing the work up with our partners," he said. "We're going to be doing it as soon as possible."

In the call, the agency also shed light on why VW's fix might take up to a year. The automaker's pool of four-cylinder diesel vehicles from the 2009-2015 model years span three generations of diesel emissions systems: an earlier system with nitrogen-oxide traps plus two generations with urea (AdBlue) injection. The urea systems should have fixes relatively soon, Grundler said, but the earlier systems with nitrogen-oxide traps "will require additional engineering" that could drag out the process.

The EPA "cannot say at this point" whether the fix will encumber fuel economy, Grundler added.