[bwilson4web]

Hi,

Toyota 'run-away accelerations' were all the rage two years ago. All sorts of "news" from the various entertainment companies that live by the motto,"If it bleeds, it leads." So the NHTSA and NASA went to work to get the facts and data:

NHTSA-NASA Study of Unintended Acceleration in Toyota Vehicles

I was looking for something else and came across data that had been embargoed but is now released:

• investigation of 58 incidents March-August 2010 - only one Prius in the list of 58, sadly, no vehicle accident data from the Prius. After all the media, I had an impression that Toyota Prius and other hybrids were running rampant all over the place. As expected, the data shows older drivers seem to be over represented in these samples.
• detailed vehicle electronic data records - I haven't read every incident, it has over 400 pages of detailed data, but gosh darn, the hardware recorded data pretty well shows driver perceptions are as reliable as any other manual process. Yes, we do find maximum accelerator and no-brake applications throughout the data . . . significantly . . . this is not unexpected.

I've followed Prius safety closely, driven by the data (or sometimes the absence.) Only I've been disappointed when a mote, Prius-pedestrian accidents, was blown into legislation while real fatalities from lane departures and failure to stop, have been and continue to be ignored. It is madness that since 2009, a very small number of the most expensive Prius have had the option of accident avoidance technology . . . technology that the accident data clearly shows would save lives. In contrast, my Congressman, Senators and President signed into law S.841 that "bells the hybrid" and has no credible life saving aspects (even the NHTSA data only referenced 'injuries.') But Toyota does not have clean hands in this bloody mess . . . accident avoidance remains a premium only vehicle option.

My career, my life, has always been driven by the scientific method. Facts and data have been my friends even when it means I must change my opinions. But in this case, there is blood on the hands of those who should have known better and sad to say, it doesn't look like 2012 will be much better . . . with one exception: The Cameron Gulbransen Kids and Cars Safety Act.

We have begun the implementation phase of this safety legislation that will all but mandate backup cameras. Last year, I bought and installed a backup camera in our 2003 Prius. Although it needs one tweak, angling the camera down for better close-view, it is an improvement over mirrors and trying to see through the sheet-metal roof supports.

Based on the law, drivers MUST be able to see directly behind an automobile whenever an automobile is shifted into reverse. The regulations would be phased in over a subsequent 4 years, starting with 10% of new cars sold by Sept. 2012; 40% by Sept. 2013 and 100% by Sept. 2014 (Cameron Gulbransen Act).

http://letsyada.com/index.php?id=resources

Bob Wilson

[bwilson4web]

My apologies, I stand corrected!

The EE Times article,"Toyota accelerations revisited-hanging by a (tin) whisker," brings a plausible hypothesis to explain a small set of run-away accelerations. In 2010, Dr. Gilbert used a decade resistor box to demonstrate to ABC how two faults could lead to runaway acceleration. Having two faults is very rare, especially when there are narrow resistance bands but tin whiskers provide a credible way this can happen.

My thanks to Doug Schaefer who shared this with the "Prius Technical Stuff" list. Doug had developed an accelerator cleaning mechanism to refurbish these accelerators. I had carried his effort until recently. Now we have a report from NASA's Goddard Space Flight Center,"Accelerator Pedal Position Sensor Caused by a Tin Whisker and Discussion of Investigative Techniques Used for Whisker Detection" by Henning Leidecker, Lyudmayla Panashchenko, and Jay Brusse of a 2005 Toyota Camry accelerator.

If the pedal is depressed quickly, then throttle is limited to 15 degrees

If the pedal is depressed slowly, then throttle can jump to 15 degrees, and further pedal application can achieve wide open throttle

Although the vehicle would operate, we did not consider it to be driveable

This new information by no means explains all the accelerator faults. Rather it suggests that past accelerator incidents need to be re-examined with careful accelerator analysis. In particular, we need improved whisker detection and application of mitigation strategies. As for those who have paid for a $500 accelerator replacement, I think a refund is in order. Equally important, this is a safety issue and a general recall is appropriate. The Goddard "tin whisker" web site discusses several mitigations but I think Professor Gilbert deserves thanks and new respect for his work.

Bob Wilson

[GeorgiaHybrid]

Bob,

I still think that 99% of the "run-away accelerations" were bogus reports either by someone wanting Toyota to pay for their screw-up or to get out from under a car payment by claiming that and hoping to get Toyota to roll over and pay the car off. I think it it is very telling that as soon as it came out that Toyota could read the computers and were giving the government that capability, all of a sudden, the instances stopped.
Before that point, you would hear of them daily. How long has it been since you heard of a "run-away acceleration" of a Toyota in the past 6 months?

[bwilson4web]

GeorgiaHybrid said:

. . .
I still think that 99% of the "run-away accelerations" were bogus reports either by someone wanting Toyota to pay for their screw-up or to get out from under a car payment by claiming that and hoping to get Toyota to roll over and pay the car off. I think it it is very telling that as soon as it came out that Toyota could read the computers and were giving the government that capability, all of a sudden, the instances stopped.
Before that point, you would hear of them daily. How long has it been since you heard of a "run-away acceleration" of a Toyota in the past 6 months?

I'm not so sure it is malice as much as human frailty. I do follow accidents and run-away acceleration events are still showing up in the news but typically they are large vehicles, SUVs and full size cars, that run into buildings while trying to park.

The one metric we have of the Toyota acceleration accidents is at least 89% of the recorded data incidents showed no brake application. This wouldn't be the first time that one intermittent problem, operator error hitting the accelerator instead of the brake, masked another, random whisker shorts in the encoder.

After reading a bit more, there is a directly applicable photo at:
http://nepp.nasa.gov/whisker/referen...app-sensor.pdf
pp. 17

This photo clearly shows tin whiskers in a Camry, dual-pot, accelerator. One whisker put a randomly inserted resistance between the connectors that attach to the resistive traces. Note that the Camry has all six terminals in a row so the opportunity for a whisker bridging the two pots is limited. The end two terminals have only one adjacent terminal and the four in the middle have two, one on each side.

In contrast, the Prius encoder has a matrix, two rows of three terminals. The four corner terminals have three neighbors and the two inner terminals have four neighbors:
http://groups.yahoo.com/group/toyota...111172780/view

So I have a failed encoder and decided to make some tests:

pins - resistance
1-5 - 116.0-108.4 ohms varies by itself
1-4 - 2,785 ohms
4-5 - 2,910 ohms
1 -> the wiper lead

3-2 - 436 ohms
2-6 - 2,484 ohms
3-6 - 2,728 ohms
2 -> the wiper lead

1-2 - .161 nF

So I used a 16VDC source walked across all combinations between pins 1-6:
1-2, 1-3, 1-4, 1-5, 1-6
2-3, 2-4, 2-5, 2-6
3-4, 3-5, 3-6
4-5, 4-6
5-6

Then I remeasured the pots:

1-5 - 20.8 ohms (was 116-108 ohms but changing)
1-4 - 2,792 ohms (was 2,785)
4-5 - 2,807 ohms (was 2,910)

3-2 - 457 ohms (was 436)
2-6 - 2,502 ohms (was 2,484)
3-6 - 2,726 ohms (was 2,728)

1-2 - .172 nF

Notice that application of 16 VDC to all pins resulted in a 5 fold reduction in the resistance between pins 1-5 and it stopped wandering right afterwards. This strongly suggests something with a variable, 80 ohm resistance 'disappeared.' I have two other, failed accelerators that I need to test.

Bob Wilson

ps. Initially: 1-5 - 20.8 ohms (was 116-108 ohms but changing)
The next morning, it became 22.4-23.0 using min/max function.
Application of over voltage is NOT enough to effect a permanent fix of this encoder.

pps. The 16VDC power source is a poorly regulated wall wart rated at 12VDC @600 ma.

[GeorgiaHybrid]

Bob,

The NASA report had one issue that was stated on page 7 that bears further consideration. The pedal they tested came from a car with a diagnostic code (one that set the MIL indicator AKA "Check Engine Light"). Every instance that I have read about with a defective pedal assembly mentioned the MIL being set. For the reported "unintended acceleration" events, none of them mention that the MIL indicator is on nor did any after action reviews.

The software uses both potentiometers and compares them to each other. In an anomaly, the computer will set the MIL light if the expected resistance if different on one or both of them. The car is still able to function (although not very well) and therein lies one issue in that the ECU should disable the car if that condition is encountered instead of using the 15% max increment increase in the throttle position.

The whisker problem is a legit issue but even then, letting off of the accelerator and applying the brakes will stop the car. Time will tell however if the news people take this up again and let hysteria run rampant in the press.

[bwilson4web]

GeorgiaHybrid said:

. . .
The NASA report had one issue that was stated on page 7 that bears further consideration. The pedal they tested came from a car with a diagnostic code (one that set the MIL indicator AKA "Check Engine Light"). Every instance that I have read about with a defective pedal assembly mentioned the MIL being set. For the reported "unintended acceleration" events, none of them mention that the MIL indicator is on nor did any after action reviews.

I'm having trouble finding "MIL" indicator on page 7 of the GSFC report titled "Accelerator Pedal Position Sensor Caused by a Tin Whisker ...":
http://nepp.nasa.gov/whisker/referen...app-sensor.pdf
It might be my new Lasik eyes . . . I have to use reading glasses now.

I think we are seeing two, intermittent faults; (1) human error, the most common, and; (2) non-zero probability of tin whisker fault that happens to correspond to the Gilbert protocol. In this case, the human reported (pp. 13):

I HAVE A 2003 CAMRY. ON NOV. 8, 2009 I HAD A VERY BIG PROBLEM WITH THE ACCELERATOR. WHEN STEPPING ON THE GAS PEDAL I COULDN'T GET ANY GAS, AND THEN THE CAR WOULD JERK FORWARD AT A RAPID RATE SO THAT I HAD TO APPLY THE BRAKES. IT WAS TOTALLY UNDRIVABLE.

GeorgiaHybrid said:

. . .
The software uses both potentiometers and compares them to each other. In an anomaly, the computer will set the MIL light if the expected resistance if different on one or both of them. . . .

Gilbert showed it is possible to set one resistance between the two that does not set an error code. Then a second resistance can command full acceleration. Sad to say, Gilbert did not know about the 'tin whiskers' which provides a non-zero possibility of it happening.

GeorgiaHybrid said:

. . .
The whisker problem is a legit issue but even then, letting off of the accelerator and applying the brakes will stop the car. Time will tell however if the news people take this up again and let hysteria run rampant in the press.

This time I don't think we'll have to deal with press re-enforced, panic. They will consider it "old news" and I suspect only serious people will consider what is going on. ... and some ambulance chasers.

Toyota should bless whoever put in the accident recording software in their airbag system. It will give them a powerful defense against lawyers who think they will be able to leech Toyota. The only risk is IF a lawyer is able to get an electronic accelerator that when swapped into a perfectly OK car . . . runs away. Well that would be bad.

Bob Wilson

[GeorgiaHybrid]

Bob,

Sorry about that...They call it a "diagnostic trouble code". You run a diagnostic on a car with a "MIL" which is short for "Malfunction Indicator Light" or 'Malfunction Indicator Lamp" otherwise known as a "Check Engine Light". Once it is lit, you will have codes that are set and possible codes that are "pending". I know that you have done a lot of that....

I just got used to calling it a MIL for short a long time ago as most of the manuals out there refer to them that way.

[greenway]

Wow, i didn't know that data like this are available for regular person, it seems really interesting, thanks a lot for sharing it.