Chrysler announced last month it would install trailer hitches on about 1.56 million 1992-98 Jeep Grand Cherokees critics said were at risk of fires in rear-end crashes because the gas tank is mounted behind the rear axle.
However, Chrysler told the National Highway Traffic Safety Administration in a 27-page statement: "The trailer hitch cannot, and will not, mitigate the risk of the high-energy rear collisions identified in your recall request letter."
The fix would only be effective in low- to moderate-speed, rear-end collisions, the automaker said.
Chrysler initially refused to comply with the government's recall request for the Jeeps, but relented after outgoing U.S. Transportation Secretary Ray LaHood met with Chrysler Chief Executive Officer Sergio Marchionne.
LaHood later defended Chrysler's proposed fix at the National Press Club in Washington.
"I don't think anybody in America can criticize us," LaHood said. "The idea that we didn't do enough or that Chrysler didn't do enough is nonsense. It goes against everything we believe. They proposed a fix and they are doing a fix. We believe the fix will keep people safe."
That's not enough for the watchdog Center for Auto Safety. Clarence Ditlow, the group's head, and former NHTSA chief Joan Claybrook joined other safety advocates at a meeting with current NHTSA Administrator David Strickland to ask that more be required of Chrysler than installing trailer hitches on some older Jeeps.
"It would be irresponsible of NHTSA not the require Chrysler to do an agency-witnessed crash-test of Chrysler's proposed remedy, given its effectiveness is highly questionable," Claybrook said after the meeting with senior NHTSA officials.
NHTSA said its data indicated there have been 51 deaths in rear-end accidents involving older Jeeps in which gas tanks ruptured and caught fire.
Ditlow said the crash-test should use the more rigorous standards that went into effect for 2007 model vehicles.
"We're confident the crash will fail," he told The Detroit News. He has proposed a metal plate be installed beneath the plastic gas tank to shield it from damage in high-speed impacts.
NHTSA said its investigation remains open "pending completion of the agency's review of the remedy announced by Chrysler."
Honda, General Motors join forces to develop fuel cell vehicles
The fuel cell remains the Holy Grail for auto engineers, a clean energy technology that uses hydrogen as fuel to produce electricity with only water vapor and heat as byproducts.
Honda has experimented with about 100 zero emission FCX and Clarity vehicles available only for lease and is expected to introduce a new hydrogen fuel cell car in Japan and the United States in 2015. GM's 118 hydrogen-fueled Equinox SUVs have logged more than 3 million miles in the last six years.
"We have complementary technologies, and by pooling them we can move development along faster," GM Vice Chairman Stephen Girsky said when the companies announced a partnership to develop next-generation fuel cell vehicles.
The race is on.
In January, Ford joined Renault-Nissan and Germany's Daimler AG in a similar fuel cell development deal with a goal of putting affordable fuel-cell powered vehicles on the road by 2017. Toyota has linked up with BMW with a 2015 target, and both Hyundai-Kia and Volkswagen are developing fuel cell vehicles independently.
Tuesday, GM joined Honda to announce the automakers would share technology for a fuel cell power train to debut by the end of the decade. The arrangement will allow the companies to share costs and cut development time.
The hydrogen fuel cell vehicles would have about the same range as a comparable gasoline-powered vehicle, but would run on non-polluting electricity. Current all-electric vehicles have been plagued by range anxiety -- worries of running out of battery power.
The Obama administration threw its support behind electrics and continues to champion all-electrics and plug-in hybrids despite disappointing sales. GM and Nissan recently cut prices and expanded incentives for the plug-in Chevrolet Volt and all-electric Nissan Leaf to boost sales in June.
GM sold a record 2,698 Volts last month, up 53 percent from a year ago, and Nissan sold 9,849 Leafs from January through June, more than it sold in all of 2012. Honda sold 208 Fit EVs in June compared with just 83 from January through May.
GM is relocating its fuel cell research and development center from Rochester, N.Y., to Pontiac, Mich., the Detroit Free Press said.
Also part of the partnership is working with energy suppliers and local and state governments to develop an infrastructure of refueling stations offering hydrogen gas.
"We are convinced this is the best way to develop this important technology, which has the potential to help reduce the dependence on petroleum and establish sustainable mobility," GM Chief Executive Officer Dan Akerson said in a statement.
How fast is the new 'Vette? Very fast
Chevrolet recently announced the all-new 2014 Chevrolet Corvette Stingray equipped with the optional Z51 performance package can accelerate from a standing start to 60 mph in 3.8 seconds.
The sports coupe can cover a quarter mile in 12 seconds with a top speed of 119 mph.
That's wicked fast so it's comforting that the seventh-generation 'Vette will be able to come to a complete stop from 60 mph in 107 feet.
At the heart of the new Corvette is a new 455 horsepower LT1 6.2-liter V-8 with performance exhaust system. The $2,800 Z51 performance package includes an electronic limited-slip transmission, cooling and aero package to improve stability.
Notable deaths of 2014 [PHOTOS]