By Kim Smiley
General Motors Co has announced a recall of over 69,000 full-size trucks and vans because of steering column defects that may allow a parked car to roll away. Only about 1 in 1,000 of the recalled vehicles is expected to have the defect.
This issue can be analyzed by building a Cause Map, or visual root cause analysis. A Cause Map is an intuitive way to visually show the cause-and-effect relationships between the many causes that contribute to an issue. In this example, the recall was announced because there are a large number of vehicles that need to be inspected. The inspections are necessary because some vehicle need to have the steering columns replaced. The replacements are necessary because a small percentage of vehicles have defective steering columns that may allow a parked car to roll.
Investigation into the steering column defects found that there were two separate issues causing similar problems. There is a possibility that the column lock module assembly might malfunction because of a manufacturing issue with a component. Investigators also found that some shift cables had been fractured because of mishandling. Both issues resulted in the same potential safety issues. If the steering column defects are present a parked car could roll away because it may be possible to shift from park when the key is removed or in “off” position, shift from park with application of brake pedal with key in “off” position, or to turn the key to the “off” position and remove while not in park. To view a high level Cause Map of this issue which includes all these causes, click on “Download PDF” above.
Once the Cause Map is built, the final step in the process is to determine a solution to prevent recurrence. Once the problems were identified the solution was fairly straightforward. The recall was initiated to inspect all vehicles potentially affected by these issues and replace the steering column if a defect is found.
A recall is never a good thing for a company, but one silver lining in this incident is that the company identified the problem during an audit before receiving any reports of issues. There have been no reports of accidents or injuries caused by these steering column defects. The majority of the vehicles are also believed to be either in transit to dealers or sitting on dealer lots so a limited number of customers should be impacted by the recall.