The safety agency began an investigation, called a preliminary evaluation, last November. After Toyota provided additional information, the agency decided the problem was serious enough to upgrade the investigation to an “engineering analysis.”
The agency said its concern is that “the engine can stall without warning at any speed and not restart.” It said it has 163 complaints from consumers.
In one of those complaints, the owner said the stalling almost caused an accident. “I was driving 60 m.p.h. on the freeway and was almost hit from behind. Another time I was turning left at an intersection and just made it through, but cars were honking and about to hit me.”
Toyota said it had reports of six accidents, but no injuries. The focus of the investigation is the engine control unit module, or E.C.U., the computer that controls the engine. The company said it did not consider the problem to pose “an unreasonable risk to motor vehicle safety.” But the automaker did note “we understand that some customers have been inconvenienced by engine E.C.U. failure and some have reported engine stalling.”
The safety agency also has many stalling complaints from owners of the Pontiac Vibe — a mechanical sibling of the Matrix — but the documents detailing the investigation do not mention the Vibe.
Toyota told the safety agency there were two possible causes of the problem. One is cracks forming on the soldered joints of the control module’s circuit boards. The other is a defect in the coating applied to the circuit boards.
In responses to questions posed by the agency, Toyota said it began investigating the problem in November 2005 and made an improvement to the control module starting in June 2007. It also issued four technical service bulletins to dealers telling them about the problem.
The agency said the module failures could lead to problems that include stalling, the failure of the engine to start or harsh shifting.
Some of the owners who filed complaints said the automaker refused to help them. “Dealer informed me there is a T.S.B. from Toyota and it is a known issue and common problem,” wrote one, referring to a technical service bulletin. “My car is out of the eight year or 80,000 mile warranty, so it would be around $1,000 to fix. Frustrated as this is a known issue which has seriously safety concerns and I have to pay $1,000 to fix their issue.”
Toyota told the agency it had approved 4,200 warranty claims involving the electronic control module. Brian Lyons, a Toyota spokesman, said the automaker was cooperating with the agency.
This is not the first time Toyota has had problems with its electronic control modules. In March 2006, Toyota sent dealers a technical service bulletin about a transmission problem in 2001-3 RAV4s. A malfunction of the module in those vehicles caused harsh shifting that could damage the transmission. Earlier this year, under pressure from the California Air Resources Board, the automaker offered a nationwide, extended warranty for the problem and said it would reimburse owners who had the repairs.
N.H.T.S.A. never investigated the RAV4 problem despite more than 300 complaints from owners, many of whom said they almost had accidents when their vehicles failed to accelerate as expected.
For more information or to file a safety complaint, go to the government Web site.