by Kim Smiley

On September 29, 2009, Toyota/Lexus issued a safety advisory that some 2004-2010 model year vehicles could be prone to a rapid acceleration issue if the floor mat moved out of place and jammed the accelerator pedal. Although the recall is only applicable in the U.S. and Canada because of the type of floor mats used, over 4 million vehicles are affected by the recall.

Although all the solutions to this problem have not yet been implemented, we can look at the issue so far in a Cause Map, or visual root cause analysis. First we define the problem. Here we could consider the problem the recall, or the acceleration problems. We can list all the models and years that are affected by the recall, and that the recall is limited to the U.S. and Canada.

We define the problem with respect to the organization’s goals. There have been at least 5 fatalities addressed by the National Highway Transportation Safety Administration (NHTSA), though some media outlets have reported more. Additionally, the NHTSA has reported 17 accidents (again, some claim more) and has received at least 100 complaints. The fatalities and accidents are impacts to the safety goal. Complaints are impacts to the customer service goal. The recall of more than 4 million cars is an impact to the production/schedule goal, and the replacement of the accelerator pedals and floor mats as a result of the recall is estimated to cost $250 million, which is an impact to the property goal.

Once we’ve completed the outline, we can begin the Cause Map, or the analysis step of the process. The fatalities are caused by vehicle crashes resulting from a loss of control of the vehicle. The loss of control is caused by a sudden surge of acceleration, inability to brake, and sometimes an inability to shut down the engine of the car. Toyota says the sudden bursts of acceleration are caused by entrapment of the accelerator pedal due to interference from floor mats. Toyota refutes the possibility that there may be a malfunction in the electronic control system, saying it’s been ruled out by Toyota research.

The vehicles are unable to brake because the brake is non-functional when the accelerator pedal is engaged, as it is in these cases. Additionally, owners whose models are equipped with keyless ignition cannot quickly turn off their ignition. These models require the ignition button to be pressed for 3 seconds to prevent inadvertent engine stops, and the instructions are not posted on the dashboard, so owners who weren’t meticulous about reading (or remembering) instructions from the owners’ manual may not know how to turn off the car while moving at very quick speeds.

When the Cause Map is complete to a sufficient level of detail, it’s time to explore some solutions. In this case, the permanent solutions (which will reduce the risk of these accidents most significantly) to be implemented by Toyota are to reconfigure the accelerator pedal, replace the floor mats, and install a brake override system which will allow the brakes to function even with the accelerator pedal engaged. However, designing and implementing these changes for more than 4 million cars will take some time, so owners of Toyotas require interim solutions. Interim solutions are those that do not sufficiently reduce the risk for long-term applicability but can be used as a stop-gap until permanent solutions are put in place. In this case, Toyota has asked owners to remove floor mats, and has put out guidance that drivers who are in an uncontrolled acceleration situation should shift the engine into neutral, which will disengage the engine and allow the brake to stop the car.

View the high level summary of the investigation by clicking “Download PDF” above.

Learn more about the recall at the NHTSA website.