Toyota's recall fix involved unspecified changes to the vehicle's software. Toyota has not said exactly how the software reduces overheating, and its statement did not answer questions submitted by The Times about whether it could affect the vehicle's performance, fuel economy or emissions. Some automotive experts contacted by The Times say the software could affect the vehicle's performance.
Toyota was aware of the inverter defect even before issuing the Prius recall, according to the suit. It began two smaller recalls of its Highlander sport utility vehicles, covering 2006 to 2010 models, about a year before the Prius recall to remedy overheating problems in a nearly identical inverter. In the Highlander recall, the inverter was replaced, the lawsuit said.
Hogan's suit and complaint alleges that the software fix was a cheap way out that failed to remedy the problem.
Hogan asserts in his letter to NHTSA that the manufacturer has sold more 800,000 Prius models in the U.S. with defective inverters and 80,000 hybrid Highlanders with the problem. The software fix costs $80, while an inverter replacement costs more than $2,000 per vehicle. Hogan said the software fix is saving the company $1.3 billion as compared with replacing the inverters.
Toyota's statement Tuesday defended the validity of the software fix, which it said allows a vehicle to move at a slow speed even if the inverter overheats and fails.
"Toyota stands behind the effectiveness and appropriateness of the Prius inverter recall remedy, which was designed to ensure operation of the vehicle in failsafe driving mode in the unlikely event of an inverter failure," the company said. "Once in failsafe mode, the vehicle can be safely driven for some distance at a reduced speed. This feature, which is common across the automotive industry, was designed to enhance vehicle safety."
When the inverter fails, the car's diagnostic system notifies the driver with a "check hybrid system" light on the dashboard and stores diagnostic codes that allow technicians to find the problem. Technicians who work for Hogan told him that all of the inverters returned with such codes have shown signs of soot and charring inside the inverter housing.
Martha Anderson, a retired school teacher who lives in South Orange County, said she was driving home from shopping last October when her 2012 Prius -- which had the software fix -- lost power in busy traffic on Alicia Parkway in Laguna Nigel. She was able to pull over into a parking space on a side street.
"I've never lost power before," Anderson said, adding that the experience left her shook up. "I just thought, 'Please, God, let me out of here.' I was lucky I wasn't on the freeway."
When the car was towed to Hogan's nearby dealership, mechanics found that the inverter had overheated so badly that two holes were blown through the aluminum case and even steel bolts had signs of melting. Anderson got rid of the Prius and bought a new Corolla from Hogan. The failed Prius is one the dealer refuses to resell.