General Motors Co last month recalled millions of vehicles with three different designs of ignition switches that could accidentally turn off the engine and disable air bags in a crash. But the automaker has concluded that more than 2 million other vehicles having exactly the same switches are safe.
The vehicles which have not been recalled include fullsize crossovers such as the Buick Enclave and Chevrolet Traverse made from 2007 to the present, which share a switch with recalled late-model Chevrolet Camaros and Cadillac CTSs. Two other switch designs are in other sets of vehicles.
GM spokesman Alan Adler said that factors including the kinds of suspension used in different vehicles could explain why a switch that accidentally turned off in one type would not turn off in another, but he said there was no single reason.
The National Highway Traffic Safety Administration (NHTSA), the auto industry regulator, is "in communication with GM about this," the agency told Reuters, without describing what it said to GM.
Former NHTSA head Joan Claybrook said GM, which has recalled nearly 15 million cars this year over switch issues, has not explained precisely why a single switch design would work differently in different vehicles and that it should release the results of vehicle safety tests so that consumers and independent engineers can review them.
Crash data submitted by GM to federal regulators did not appear to show an unusual number of fatalities for the unrecalled cars.
The unrecalled models passed eight "dynamic" tests, such as driving over potholes with a key weighed down by a heavy key ring, and additional tests, including one to see if the switch and key can resist turning off when bumped by a driver's knee, GM's Adler said. Recalled vehicles failed.
"We do not believe there is an unreasonable risk to motor vehicle safety in vehicles we did not recall," Adler said.
Sheryar Durrani, a former NHTSA project engineer who has worked as an engineering consultant for the auto industry, said design differences, including the location of the ignition switches and keys, could mean the need to recall some vehicles might not be as high as for others.
Durrani reviewed a description of GM's tests and said that without a full and public explanation of why switches failed in the recalled vehicles but not in other vehicles, GM left unclear whether it had found "the true root cause of the failure."
A GM engineer in a 2005 internal email