One for the (Reliability) Books
Guest post by Kirk Gray
The GM Ignition switch failure case history should be required reading for all reliability engineers.
It is rare to have insight into any internal company history of serious electronic and electromechanical failures. Failure analysis and the causes of electronics or electromechanical systems failure can be a difficult investigation for any manufacturing company. Disclosure of the history and data is rarely if ever published due to the potential liability and litigation costs as well as loss of reputation for reliability and safety.
The report of the probe by former U.S. Atty. Anton Valukas issued June 2014 by the NHTSA on the failure of GM to determine the failure of air bags to deploy due to an ignition switch assembly is a fascinating case history. If you would like a copy of the redacted full 325 page report you can download it here.
The NHTSA report will become a classic case study for management and reliability engineering history books. Anyone who has worked for a large product manufacturing company likely will relate to many aspects of the mismanagement, misdirection, and company silos of information that prevented in understanding and action for this fatal flaw in certain model years of the Cobalt and Ion models ignition switch.
The NHTSA report to GM shows multiple reporting errors, mismanagement of leadership in investigations, lack of data sharing, and lack of individual responsibility among other many other complications. What is also very interesting about the NHTSA report is the many different memories of meetings and investigations and the lack of documentation of what was or was not communicated during those meetings.
Of course a major player that misleads the failure investigation was Ray DeGiorgio, who led the team that developed the switch and later approved a change to the part. Unfortunately and against GM procedures the part number was not changed, and DeGiorgio repeatedly denied making and approving a change to the spring and detent plunger that later improved the switch torque and eliminated the failures.
In the end, simple testing and empirical measurements of the torque required limits, and comparison of those limits clearly showed the ease at which the switch could be moved from the “Run” position to the “ACC” position. It would appear from 20-20 hindsight the problem would have been discovered if any engineer involved in the investigation had gone out to used and new car dealers or a junkyard and actually measured the torque required to rotate the switch between “Run” and “ACC” position in the different Cobalt model years that the issue was and was not seen. This was eventually done, but only years later and at first unintentionally.
During design development of the switch it is almost certain that the low force to move the switch would be found in a step stress test with vibration, key chain weight and temperature. It seems that actually testing of the device was a low priority throughout the years of investigation. Instead of using stress testing and comparing switch torque limits, GM tried reproducing the issue by simulating a worst case rough road driving test track but were unable to. Testing several samples of switch assemblies to an empirical boundary or limit, would have had a better probability of showing design flaw over an attribute test of pass or fail for a few samples on the “teeth chattering” test track.
It all reminds me of a quote from two known car experts and MIT Engineering graduates, Tom and Ray Magliozzi, who once on their NPR radio show “Car Talk” warned to be cautious of MIT Engineers understanding of actual devices operation because “they are never shown the actual ‘thing’ but are only given the mathematical models that describe the ‘thing’”. In the story of the GM Cobalt ignition switch there seemed to be little actual observation, testing, or empirical measurements on a device that would seemingly not hard to access since thousands were built and in used and new car lots.
You can see many photos of the GM ignition switch assembly at the root of the problem from McSwain Engineering, Inc. at the International Business Times website link here.
It took a plaintiff’s investigator to physically compare ignition switches from Cobalt model years that had the problem and the years after the switch was changed and the issue did not occur. Of course the denial of the design change by the DeGiorgio that approved the change caused misdirection of the investigation for years by denying the change that fixed the problem was made.
Some of the most interesting findings were
One newspaper review of the Cobalt in 2005, the reviewer Gary Heller of the Sunbury Daily reported that “unplanned engine shutdowns happened four times during a hard-driving test last week…I never encountered anything like this in 37 years of driving and I hope I never do again”
A Wisconsin State Trooper, Keith Young, correctly identified the problem back in 2007, seven years before GM accepted the cause.
Lack of knowledge of the many GM engineers and investigative teams looking at the “moving stall” issue is that the ignition switch in the “ACC position” prevents deployment of the airbags; therefore the switch problem was only considered an “inconvenience” and not a safety issue. In the report it states that “The engineers made a basic mistake. They did not know how their own vehicle had been designed and GM did not have a process in place to make sure some looking at the issue had a complete understanding of what the failure of the ignition switch meant for the customer”.
A proliferation of committees at GM made disavowal of responsibility easy. Some of the interviewed witnesses called the “GM salute”, a crossing of arms and pointing towards others, indication that the responsibility for the issue belongs to someone else. There was also described the “GM nod”, that is when everyone nods in agreement to a proposed plan of action, but then no one really does anything to act on the plan.
The ignition switch was redesigned and parts of the assembly were changed to improve the torque required to hold the switch positions, unfortunately the part number was not which added to the delay in discovery of the change.
GM Issued a Technical Service Bulletin about the problem in 2005 and 2006. Trooper Young found them online at the NHTSA back in 2007
The GM Field Performance Assessment (FPA) engineers did not consider searching for information relevant to the problem of airbag deployment that was publicly available or in GM’s own files.
After on Engineer unintentionally notice how extraordinarily easy it was to turn the key on one of the Cobalt model vehicles in a junkyard when they were trying to retrieve a BCM (Body Control Module) the Engineers went to a local fish and tackle store to purchase a fish scale in order to measure the torque on the switches required to move it from the run position to the ACC position in “a number of Cobalt vehicles at the junkyard”.
In the Reports assessment of GM culture, many other interesting factors were discussed.
In critical safety meetings, amazingly no one took notes. The general avoidance of taking notes was seemingly communicated among GM engineers through “urban lore”, as there was no evidence that any lawyer or manager at GM ever gave that instruction. The result was that there were no clear records of attendance, or what was discussed or decided.
The last parts of the report detail the cultural and systematic failures of GM and actions to prevent the same failure of corrective action for a safety issue that occurred with the ignition switch. We can only wait to see if the culture and policies at GM that caused this fatal flaw to be uncorrected for so many years will change.
What aspects of the GM culture and systems that caused this failure to find root cause and implement corrective action have you seen in companies you have worked for?
2 thoughts on “Required Case History for Reliability Engineers”
Good post. The problem actually was occurring before the Cobalt I believe. I had a 90’s vintage Chevy Cavalier that I had to replace the ignition switch for the above cause. I was told to not have any heavy items on the Key chain as that would cause the switch to move out of run. The problem never reoccurred after the new switch was installed (and the wife removed some of the dodads from her key chain).
As we are finding out now that you are correct, the problem was occurring with many GM models since I first wrote this blog.
It is always puzzling why GM (and many other reliability engineers I know) are not motivated to actually test, measure, or examine the actual physical assembly until it reaches the customer and is a field problem.