NEW YORK (CNNMoney.com) -- Millions of Toyotas -- some of them among America's most popular cars -- are under scrutiny as the result of two separate recalls, both involving problems with the gas pedal.
Here is what Toyota owners need to know as the carmaker scrambles to find a fix for the problems.
How big is the problem? All major auto manufacturers have gotten at least some complaints of "unintended acceleration" in their vehicles. According to a December 2009 analysis by Consumer Reports looking at a federal database, Toyota has received a disproportionate number of complaints.
How many deaths have there been? In the past 10 years, according to some analyses, there have been 19 deaths in Toyota vehicles connected to some form of unintended acceleration, a figure that the National Highway Traffic Safety Administration calls "plausible" based on its data.
Similar statistics have not been provided for other automakers, so there's no way to know how Toyota compares to other major automakers in this regard.
Four of those deaths occurred in a single incident: the August 2009 crash that killed an off-duty California Highway patrolman and his family in a Lexus, the agency said. That crash was caused by the car's accelerator pedal getting stuck in a non-standard floormat, the sort of problem that was the subject of a recall initiated in November.
Toyota's recalls cover only later model-year vehicles even though unintended acceleration cases were under investigation going back about a decade. NHTSA investigators were unable to identify any vehicle defects in the earlier incidents.
Unintended acceleration is hard to definitively confirm because it's impossible to rule out driver error in many cases.
Which cars are involved? The stuck-pedal recall of 2.3 million vehicles announced last week affects Toyota's 2009-2010 RAV4, Corolla and Matrix models; the 2005-2010 Avalon; 2010 Highlander; 2007-2010 Tundra and the 2008-2010 Sequoia; and some 2007-2010 Camrys (only those with gas pedal assemblies made by a specific Toyota supplier; your dealer can check). No Lexus or Scion models are involved.
What's the sticky-pedal recall for? Over time, gas pedals in some of the recalled cars become sticky. At first, they just become a little harder to push down and, when you lift your foot off the gas, slower to come back up.
In the worst case, the pedal on these cars can become stuck part way down. That, of course, could mean the car keeps accelerating, or just keeps going, even after you take the foot off the gas.
This recall is separate from the one announced in November to fix a problem in which the gas pedal can get stuck in the cars' removable floor mat.
How's Toyota going to fix the sticking pedals? Toyota said Monday it has developed a fix for gas pedals and is already shipping the new parts to dealers. The fix involves reinforcing the pedal assembly in a way that eliminates the excess friction that has caused the pedals to stick, the company said in a press release. Toyota said dealers will work extended hours to fix the recalled vehicles.
The automaker will begin notifying customers this week to tell them when they can have their vehicles fixed.
What, exactly, is causing this? A lever that is part of the accelerator pedal assembly can become worn and begin to stick. This is especially true if the part becomes moist, such as when condensation occurs on a cold morning or, in some cases, if the vehicle is parked in a humid place for a long period.
What if I notice problems? If your gas pedal starts to feel sticky, stop driving immediately, Toyota says. Pull over in a safe place, then call a dealer and have them come get your car.
What if the gas pedal is really stuck? If it's stuck part way down, applying the brakes should be enough to slow the car and bring it under control. Don't pump the brakes, though. That will just weaken your power brakes. Instead, press and hold the brakes. Also, at the same time, you can shift the transmission into neutral, which will stop the engine from driving the wheels.
It's good to know what to do in cases like this no matter what type of car you drive, said Jake Fisher, senior automotive engineer for Consumer Reports magazine. Although even in cars affected by this recall, it's a rare occurrence, he said, it can happen in almost any car model as it gets older.
What if I'm not having any problems ... yet? Since the problem develops gradually over time, Toyota says, you should have plenty of warning before the pedal gets really sticky. If you're concerned, take your car to a Toyota dealer and they can tell if your gas pedal is still OK. Remember, though, there is still no prescribed remedy.
Beyond the recall, why stop making and selling all these cars? Toyota says it wants to ensure the safety of its customers and restore confidence in their brand. While that may well be true, Toyota is also under a legal obligation to stop selling cars that are under a recall, according to the National Highway Traffic Safety Administration.
Otherwise, Toyota would be filling dealer inventories with cars that needed to be fixed and couldn't be sold until they were.
What's all this about floormats? About 5.3 million Toyota vehicles are under a separate recall to fix a problem in which the gas pedal could get hung up on the car's floormats. The floormat-related recall, first announced in November, originally involved 4.2 million vehicles, and was expanded to include another 1.1 million last week.
Many of the 2.3 million vehicles recalled for the stuck-pedal problem are also under recall for the floormat problem. Toyota has not yet given a figure for how many vehicles are affected by both recalls.
What's the remedy for the floormat problem? In that case, Toyota is altering the actual pedal itself to make it shorter and, therefore, less likely to get stuck on the lip of the mat. Toyota also is replacing the floor mats in some cars.
In some Toyota and Lexus models, the automaker also is installing a "brake override" system, which immediately cuts engine power to the wheels when the brake pedal is pressed. In the meantime, Toyota is advising drivers who haven't yet had their cars worked on to remove the floor mats.
Could there be a software issue? Some analysts, unable to locate any other single cause for unintended acceleration in Toyota cars, wonder whether it might be a software problem. Like most modern automobiles, Toyotas are packed with computer chips and embedded software to control many vehicle functions.
Toyota says it has thoroughly tested the software used to control gas pedal response in its cars under a variety of circumstances, including subjecting it to various forms of radiation while in use. The carmaker says it is confident the software, for which there are also multiple back-up systems within the car, is not the source of unintended acceleration issues.
What else is Toyota doing to prevent problems like this? Toyota says it is making the brake override system standard equipment on all of its cars. The software for this feature will also be added to some cars as they are brought in for recall repairs.
Is there more Toyota could do? Some experts, including those at Consumer Reports magazine, have suggested that Toyota change how the "keyless start" system in its cars operates. In some Toyota and Lexus models, the driver can start or turn off the car without using the key by just pressing a button in the dashboard.
If one of those models were to start accelerating wildly, a driver could turn the engine off while still driving by pressing and holding that button for three seconds.
But a panicked driver, especially one who wants to keep both hands on the steering wheel of his speeding car, is unlikely to do that. Instead, he's more likely to press the button briefly but repeatedly. In a Nissan with keyless start, for instance, three presses like that would do the trick.