Tin Whiskers and Toyota: Collision Course?

New criticism of the reports by the National Highway Traffic Safety Administration and NASA Engineering and Safety Center that led the US Transportation Secretary to publicly absolve Toyota of unintended acceleration problems in its vehicles is breathing new life in what the mainstream media had decided was a closed story.

When the US agencies released their reports in February, Sec. Ray LaHood stated that the findings by the NHTSA and NASA proved Toyota’s electronics were not guilty of causing unintended acceleration. “The verdict is in,” LaHood said. “There is no electronic-based cause for unintended, high-speed acceleration in Toyotas.”

Not so fast, said Safety Research & Strategies, which this week went to press with a report condemning the earlier findings for everything from flawed analysis to conflict of interests.

In the report, SRS claims the tin whiskers found in the vehicle samples provided to NASA did in fact reveal a failure mechanism that was ignored in the NHTSA report, yet that mechanism in accelerator pedal sensor circuits can cause resistive shorts that could lead to acceleration.

The report has become a hot topic among a group of printed circuit board reliability experts, who are pointing to the “extremely small sample size” of vehicles used by NASA to perform its investigations. “There are millions of Toyotas on the road today but NASA was able to look at only a handful,” wrote Bob Landman of HRL Laboratories, on the IPC TechNet Listserv. “Despite the small sample size, they found whiskers.  The Law of Errors tells you what about this fact?  That whiskers are a significant finding.”

Landman noted that in one case, NASA found whiskers in a pedal assembly after a woman who had an incident of sudden acceleration was provided the defective assembly by the dealer that fixed her car. “She learned of the [Department of Transportation] investigation and gave them the assembly, and it found its way to NASA where [researchers] found whiskers shorting the leads of the potentiometer.

Landman also said NASA demonstrated a braking problem under a test track sudden acceleration simulation.  “A NASA driver was strapped in, a NASA passenger had two switches, one to cause sudden acceleration at 45 mph and the other to safely turn off the the sudden acceleration so the vehicle could be brought to a stop.  What happened?  When sudden acceleration was initiated, the throttle was at 100% so there was no vacuum assist and the driver, using both feet on the brake pedal, could not stop the vehicle! It was found that it would take 600 pounds of brake force on the pedal to cause the brake to slow down the vehicle. Clearly, the software does not allow the brake to override the pedal. This is a defective design.”

“Something is rotten in this [NHTSA] report, it seems to me, and SRS found it,” Landman said.

Where’s There’s Toyota, There’s Fire

The sudden unintended acceleration problems in Toyota’s vehicles have touched off a firestorm of controversy over the cause(s). Now, a professor of automotive technology at Southern Illinois University has entered the fray, testifying before Congress that the trouble locating the problem’s source could stem from a missing defect code in the affected fleet’s diagnostic computer.

In testimony before a house subcommittee  Tuesday, David W. Gilbert, a Ph.D. with almost 30 years experience in automotive diagnostics and troubleshooting, said his initial investigation has found problems with the “integrity and consistency” of Toyota’s electronic control modules to detect potential throttle malfunctions.

Specifically, Prof. Gilbert disputed the notion that every defect would necessarily have an associated code. The “absence of a stored diagnostic trouble code in the vehicle’s computer is no guarantee that a problem does not exist.”

In fact, using a 2010 Toyota Tundra, Prof. Gilbert discovered electrical circuit faults could indeed be introduced into the electronic throttle control system without setting a diagnostic trouble code. “Without a diagnostic trouble code set, the vehicle computer will not logically enter into a fail-safe mode of operation. … Since the vehicle computer will only react to defective sensor inputs outside of the range of programmed limitations if the circuit is not defective; it must be good.” In other words, because a code did not exist for the sensor to inform the on-board computer of a problem, when a short occurred the computer did not recognize the problem, and therefore it took no steps to mitigate it. And absent the code, no defect was entered into the database for post-incident tracking.

Prof. Gilbert further determined that electronic control module malfunction detection strategies were not sufficient to
identify all types of fundamental APP sensor and/or circuit malfunctions. “Some types of electronic throttle control circuit malfunctions were detectable by the ECM, and some were not,” he testified. “Most importantly, the Toyota detection strategies were unable to identify malfunctions of the APP sensor signal inputs to the ECM.” (Watch this video of Dr Griffin’s test at his university test track.)

Yikes! If Prof. Gilbert is correct, this could explain why Toyota engineers have failed to diagnose the electronics as a potential source of sudden unintended acceleration. As one reliability expert told me, this could be the smoking gun.

We await Toyota’s response to this revelation.

Toyota: ‘Electronics Not Ruled Out’

In a move that will only add fuel to the fire, a top US Toyota executive yesterday testified that the automaker has not ruled out electronics as a source of the sudden acceleration problems plaguing the company’s vehicles.

Sudden acceleration “has many, many causes,” including transmission software problems, faulty cruise control and even engine revs caused by engaging the air conditioner, he said, according to the LA Times today.

It is the first time Toyota has acknowledged publicly that the cause of sudden acceleration in certain models might be related to something other than the floormats.

To make matters worse, a professor of automotive technology claims to have found a flaw in the electronics system of a Toyota that “would allow abnormalities to occur.” Finding the flaw took about 3.5 hours, he said.

This story, against all odds, continues to get worse for Toyota. The company hired an outside firm to conduct testing on its defective cars; that company claimed the electronics were not at fault. This latest revelation — though hardly a smoking gun — just adds to the controversy that Toyota is hiding something.