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NASA Can't Find Unintended Acceleration Causes in Toyota's Electronic Throttle Control System Page 2


The NESC team did find, however, that:

"There is  a single failure mode found that, combined with driver input, can cause the throttle to jump to 15 degrees in certain conditions and may not generate a DTC [diagnostic trouble code]. This failure effect can be removed by releasing the accelerator pedal or overridden by the braking system. For the small throttle openings, the NESC team found single failure modes within the ETCS-i that can result in throttle openings less than 5 degrees. These failures may result in high idle speed, hesitation, and surging as described in submitted VOQs and may not generate DTC, but can also be removed by  releasing the accelerator pedal or overridden by the braking system. "

In concluding, the NESC team stated that:

"Proof for the hypothesis that the ETCS-i caused the large throttle opening UAs as described in  submitted VOQs could not be found with the hardware and software testing performed. Because proof that the ETCS-i caused the reported UAs was not found does not mean it could not occur. However, the testing and analysis described in this report did not find that TMC ETCS-i electronics are a likely cause of large throttle openings as described in the VOQs."

Michael Kirsch, principal engineer at the NASA Engineering and Safety Center wasquoted in the Washington Post as saying that "... our detailed study can't say it's [UA caused by some type of electronic malfunction] impossible" but rather that its "unlikely."

The only conclusion that the NESC reports seems to leave is that UA's which cannot be attributed to known mechanical problems, i.e., caused by floor mats or sticky-pedal issues, must be caused by driver "pedal misapplication."

The NHTSA report lends further support for this conclusion:

"NHTSA and NASA both reviewed relevant consumer complaints and warranty data in great detail. Both agencies noted that publicity surrounding NHTSA’s investigations, related recalls, and Congressional hearings was the major contributor to the timing and volume of complaints. Both also noted that the vast majority of complaints involved incidents that originated when the vehicle was stationary or at very low speeds and contained allegations of very wide throttle openings, often with allegations that brakes were not effective. NHTSA’s analysis indicated that these types of complaints generally do not appear to involve vehicle-based causes and that, where the complaint included allegations that the brakes were ineffective or that the incident began with a brake application, the most likely cause of the acceleration was actually pedal misapplication (i.e., the driver’s unintended application of the accelerator rather than, or in addition to, the brake)."

"The results of NHTSA’s field inspections of vehicles involved in alleged UA incidents during 2010 supported this analysis. Those vehicle inspections, which included objective evidence from event data recorders, indicated that drivers were applying the accelerator and not applying the brake (or not applying it until the last second or so), except for one instance involving pedal entrapment."

NHTSA goes on to state in the DoT press release that:

"Based on objective event data recorder (EDR) readings and crash investigations conducted as part of NHTSA’s report, NHTSA is researching whether better placement and design of accelerator and brake pedals can reduce pedal misapplication, which occurs in vehicles across the industry."


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Comment (1)
  1. The NASA study is hard to swallow in light of the many credible people who have had the problem. Is it possible that the electronics function fine in a test environment, but are affected by the presence/certain type or proximity of cell phones in the user environment. Has anybody ever examined whether a certain type of cell phone, computer, or mapping system was common to all these incidents?
    As in avionics, even though frequency interruption is rare, there must be some degree of a risk, so they ask everybody to turn off their electronic devices during takeoff and landing.
    Hard to believe that the best and brightest would not have already examined or discarded this theory by now. Just wondering.
     
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