General Motors has recalled a further 1.5 million vehicles, some for possible problems with ignitions blamed for 12 deaths.
Last month, GM called back 1.6 million cars amid questions over why it had taken years to address an ignition defect it knew about as early as 2001.
GM said there was no evidence of fatalities from ignition-related incidents in the new group of 824,000 cars being called back - Chevrolet Cobalts and HHRs, Pontiac Solstices and G5s, and Saturn Skys for 2008-2010 model years. But it added that 90,000 of the faulty ignitions were in the 2005-2007 models used as replacements in cars covered in the new recall.
GM said it needed to check all of the cars in the new action to see which ones had the potentially faulty replacement ignitions.
"We are taking no chances with safety," GM's chief executive Mary Barra said on Friday.
GM is under investigation by the US Justice Department and the US Congress over its mishandling of the problem with the ignitions, which by one count has caused hundreds of accidents.
Since 2005 GM itself has received hundreds of consumer complaints over the problem, in which a car's ignition could suddenly move into "accessory" or "off" position, cutting off electronic systems including airbags.
Airbags did not deploy in the fatal accidents recorded.
GM is now facing lawsuits over the issue, and last week US Senator Richard Blumenthal urged the Justice Department to create a fund for victims, arguing that the firm "criminally deceived" the public.
Late on Friday, GM also separately recalled approximately 490,200 pickups and SUVs over possible problems with a six-speed automatic transmission.
That recall concerns 2014 Chevrolet Silverado 1500 and GMC Sierra 1500 pickups, and 2015 Chevrolet Suburban and Tahoe and GMC Yukon and Yukon XL SUVs.