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The Toyota's Corps. sudden Acceleration Problems still unresolved.




 
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Author Topic: The Toyota's Corps. sudden Acceleration Problems still unresolved.  (Read 66469 times)
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WA1GFZ
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« Reply #100 on: March 05, 2010, 05:02:09 PM »

I've never seen a suppression diode take out a relay in 40 years.
I have seen a relay take out a driver when there is no suppression diode many times. An unsuppressed 28 volt realy can generate a 1KV pulse easily
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Ian VK3KRI
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« Reply #101 on: March 05, 2010, 05:14:44 PM »

This professor from Carnegie Mellon has been doing some digging....
check out the missing diodes from the relay circuits on 2007 Camry's...

http://www.ece.cmu.edu/~raj/toyota.html

 Huh


Interesting article, but when I went to find the authors technical background I found...
http://www.ece.cmu.edu/~raj/

"# Co-Director, General Motors-Carnegie Mellon Vehicular Information Technology Collaborative Research Lab.
# Co-Director, General Motors-Carnegie Mellon Autonomous Driving Collaborative Research Lab."

Not that I'm questioning the integrity  of gentleman, but  Buick good, Toyota bad .....

 
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WQ9E
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« Reply #102 on: March 05, 2010, 05:33:12 PM »

It is very common in academe to be associated with various companies because that is often the only way to get access to data and needed research funding.  Most of us have taken industry dollars but research integrity is very important because once gone it is gone forever.

I think his findings are interesting and note that he is not claiming that this is the root cause of failure.

It is interesting timing for me since I just finished repairing an Icom IC-751 that had an issue with a relay driver.  Icom does use diodes across the coil and the one across this particular relay had a cold solder joint from the original wave solder.  It did last quite a few years before the relay driver transistor was damaged but in this rig there is a protective diode across every relay coil to prevent this problem.

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« Reply #103 on: March 06, 2010, 12:30:22 AM »

I wonder why this paper http://energycommerce.house.gov/Press_111/20100223/Toyota.Electronic.Throttle.Control.Investigation.pdf  has been pretty much buried, in terms of discussion.

It was submitted as part of the recent congressional dogpile, but makes the case that the throttle input signals, if incorrect in certain situations, will not trigger a fault with the ECU.  It's also a poor design, since both signals track each other in slope, separated by .4V or so.  If they are shorted together, or one goes to +5V rail, the car goes to full throttle.  And the ECU doesn't know there's anything wrong.

Piss poor design.
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WD5JKO
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« Reply #104 on: March 06, 2010, 10:14:04 AM »


"It did last quite a few years before the relay driver transistor was damaged but in this rig there is a protective diode across every relay coil to prevent this problem"

     Roger,

   The diode across the relay is fine for small relays, or for relays that don't switch high current loads.
When we have big relays, or relays that switch high current loads (especially DC), the speed of the relay to open up after being energized is dependent on the speed which the coil field decays. The L/R time constant comes to play here. If you use a diode the decay is pretty slow, and if the contacts slowly open while flowing high current, then contact wear or pitting is really bad. If the load is DC, then the situation is even worse since an arc may sustain as the relay contacts open.

   So in the case of automotive power relays it is important to 'thump' them both when energizing and de-energizing to insure quick open/close of the contacts. We also don't want to switch high current with the N/C contacts either since the spring force is lower than the N/O contact force with the coil energized. Sure we need to deal with the back EMF spikes, but using a diode is not always wise.

   The GM approach with a resistor across the coil is interesting. Maybe the relay driver is a bipolar transistor with a VCEO rating of 80 volts. If they size that resistor to the relay such that the back EMF spike is limited to say 50v, then the driver is OK, and the relay will quickly de-energize because the 'R' part of the L/R time constant just got much larger.

   The Toyota approach shows no diode or resistor across the relay coil. Is this bad? Fore sure the relay will be 'thumped' such that contact wear is not an issue. If the driver is a power fet, then the back emf spike will get absorbed by the fet when the VDS value is exceeded. Since the transient is brief, and FET's are immune to secondary breakdown, no harm is done.

   But what if Toyota uses unsurpressed relays, and biplolar drivers? More bad Huh

Jim
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WA1GFZ
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« Reply #105 on: March 06, 2010, 03:58:45 PM »

OK I see, yes a resistor will reverse the magnetic field but at the expense of a high voltage spike back at the driver. This means the driver will need suppression at the device and the conductor to the coil will radiate a nice wide band transient.
Relays are pretty expensive I bet a lot of auto. switching is solid state these days.
I also bet many of the little morors are brushless. There are a number of low voltage drivers out there that work very well. The IR IPS drivers are great at 28 VDC and take digital inputs. They have overcurrent and high temperature shutdown. Too slow for RF though.
Some bipolar transistors have a built in protection diode.
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ka3zlr
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« Reply #106 on: March 06, 2010, 07:35:04 PM »

Hello,

Welp, there's absolutely not a thing to worry about...our Gov is involved very deeply in this..(I seen two guys quit and went to work for Tayoter)....They're on the scene and taking care of business man...  Grin

I feel so Safe on the roads now.....

73
Jack
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WU2D
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« Reply #107 on: March 09, 2010, 06:42:34 AM »

I bet a large number of the deaths are caused by someone else doing stupid moves.

Mostly from the Hartford CT driving academy!
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WD5JKO
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« Reply #108 on: March 09, 2010, 07:05:31 AM »



Toyota fights back!!

"To prove their point, Toyota officials revved the engines of cars made by competitors, including a Subaru Forester and a Ford Fusion, by connecting a circuit rigged up to the wiring of the gas pedals."

http://news.yahoo.com/s/ap/20100308/ap_on_bi_ge/us_toyota_recall_electronics

The many comments from the Yahoo link have some good input. Here is one:

"Toyota made one bad decision with their DBW (Drive by wire) design. They only have one DBW circuit.
GM also used DBW, but they do it with a safety mechanism. Toyota only has 1 DBW circuit, while GM has two.
Toyota has one 3 wire circuit that has a 5 volt reference, a ground and a circuit to check the voltage drop.
GM has two circuits. Both with a 5 volt reference, a ground and a circuit to check the voltage drop.

Difference is as the voltage drops on Toyota's the PCM opens the throttle accordingly, so if the wire detects 3 volts it's open 60% if the wire detects 2 volts it's open 70%, ETC.

GM has one circuit at 5 volts, and one at zero. When the 5 volt circuit drops to four the other circuit should be at 1. When the 5 volts circuit drops to 3, the other circuit raises to 2. They should ALWAYS correliate opposite each other,. If they don't the car goes into "limp mode" shutting down the acceleration and turning on the check engine light. This way the only way to possibly have unintended acceleration is by a faulty/sticking pedal or PCM. Toyota doesn't do that, so unless they can replicate the problem in their shop they can't be 100% positive of their repair. Either way, with a shim this will allow the pedal to go to closed position quicker, therefore any PCm problems that may exist will be fixed due to the throttle going back to closed position faster. I say this will fix their problem, however one could attempt to replicate this problem by slowly releasing the gas pedal at the exact same speed that the pedal used to go back up before the shim was installed. Pretty unlikely"

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W8EJO
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« Reply #109 on: March 15, 2010, 04:09:19 PM »

Last week's phony  LA "runaway Prius" story caught my attention then I read this from a March 12th article in The Atlantic:

"These "electronic defects" apparently discriminate against the elderly, just as the sudden acceleration of Audis and GM autos did before them. In the 24 cases where driver age was reported or readily inferred, the drivers included those of the ages 60, 61, 63, 66, 68, 71, 72, 72, 77, 79, 83, 85, 89--and I'm leaving out the son whose age wasn't identified, but whose 94-year-old father died as a passenger."   

Full article here:
http://www.theatlantic.com/business/archive/2010/03/how-real-are-the-defects-in-toyotas-cars/37448/

I suspect more than ever that this is just another phony "sudden acceleration" problem a la' 60 minutes Audi Bravo Sierra..
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Terry, W8EJO

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ke7trp
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« Reply #110 on: March 15, 2010, 04:32:15 PM »

Yesterday, On the way Home, I pulled into a local Convenience strore parking lot.  When I looked up, I realized that our store now stocks the toyota Prius. They have one instock right on the shelves Smiley

Some old women Drove her Prius clear into the store.

I talked to the woman crying outside in the parking lot.  She said she put the car in reverse, looked back, Hit the gas and the car went FORWARD full throttle into the Store. It crashed right through the glass and aluminum frame and then smashing into shelves of products.  I stand at that counter at least once a day. Had I been there, I would have been killed for sure. 

Nobody was hurt.  Just lots of damage.  Obviously, She put the car in Drive on accident and there is no fault with the car. She was already talking about "how that car almost killed people".  Uh, No..  YOU almost killed people. 

Its the second time someone Drove into the store.  I think its time for some concrete and steel Cylinders to be installed outfront. This would stop the cars and maybe save lots of lives.  Its common for 4 to 5 people to be standing exactly where that woman parked her car!



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flintstone mop
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« Reply #111 on: March 15, 2010, 08:45:59 PM »

I think it's time to require older drivers, getting near 70, to start taking driving tests. As they get older the tests get harder to check on reaction time and ability to think and make a decision in a certain amount of time.
The "driving tests" could be in a mock set-up with a simulated driving course.
There's too many of these "old age" accidents happening, where the "car just accelerates full throttle into grocery stores or parking lots", killing people.
I live in a small town in Western Pa. and there's a lot of old folks around and they creep along and turn on their signals WHEN they make the turn and go about 2 MPH. Some swing out to the middle of the road like they're drivng a tractor trailer to make their 2 MPH turn.
I drove an 80 passenger school bus and never swung out to make a turn.

Has any analysis ever been made that the cruise control is malfunctioning, or engaged without the driver's knowledge? Some of these cars have all kinds of buttons on the steering wheel now.

Fred
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Fred KC4MOP
WA1GFZ
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« Reply #112 on: March 15, 2010, 08:56:46 PM »

John  JN thinking about your post. If the ground side of the pot opens  the output goes to 5 volts no matter where the wiper is positioned.
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Bill, KD0HG
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« Reply #113 on: March 15, 2010, 09:42:30 PM »

I just heard that ages 50-60 Toyota drivers are reporting 'unwanted acceleration' at three times the rate of 20-30 year old drivers.

Yes, driving the same cars.

There's a scientific lesson here somewhere..
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ke7trp
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« Reply #114 on: March 15, 2010, 09:44:42 PM »

Old people cant Drive?   Shocked

C
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Ian VK3KRI
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« Reply #115 on: March 16, 2010, 08:27:53 AM »

I wonder why this paper http://energycommerce.house.gov/Press_111/20100223/Toyota.Electronic.Throttle.Control.Investigation.pdf  has been pretty much buried, in terms of discussion.

It was submitted as part of the recent congressional dogpile, but makes the case that the throttle input signals, if incorrect in certain situations, will not trigger a fault with the ECU.  It's also a poor design, since both signals track each other in slope, separated by .4V or so.  If they are shorted together, or one goes to +5V rail, the car goes to full throttle.  And the ECU doesn't know there's anything wrong.

Piss poor design.

Interesting paper, but I think you've misread this slightly.   My reading is that if the two signals are resistively coupled ( " certain short circuit resistances between VPA and VPA2 were undetectable")  AND  one goes to +5 volt rail.  This a significantly less likely than a the two signals being shorted and pulled up to 5V.

Whether or not its still a piss poor design, I'll leave to the lawyers, who'll probably end up making that call rather than engineers.

                                                                                                   Ian VK3KRI
 
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WA1GFZ
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« Reply #116 on: March 16, 2010, 08:33:21 AM »

glad these people don't have nukes
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WD5JKO
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« Reply #117 on: March 16, 2010, 09:49:47 AM »

I just heard that ages 50-60 Toyota drivers are reporting 'unwanted acceleration' at three times the rate of 20-30 year old drivers.
Yes, driving the same cars.
There's a scientific lesson here somewhere..

   Yes I agree. When I was in my twenties, all sorts of things happened to me where I SHOULD HAVE hired a lawyer and fought various issues. Instead I did nothing. Now in my 50's, I will assert myself and fight back given the same circumstances. This does not make me senile.

    On the professional front I work with some pretty high level software engineers. I find issues, and they fix them. These guys have to fight some mighty complex software issues that are often NOT easily reproduceable. Whether we are controlling a car, or other sophisticated machine, there are all sorts of software subroutines not ordinarily used when everything is behaving. This means that basic functionality will be fine, but when we step through a less traveled subroutine, if a bug exists, then that is when we have problems. So take a Toyota Prius with a host of sensors, input statuses, etc., the combinations are infinite.

    Maybe there is a combination of software conditions that leads to unwanted acceleration? Now add to this EMI susceptibility, and the "Tin Whisker" problem, and now we have a mess.

    So the Toyota engineers drove the Prius around the block, and it worked as designed. That means nothing to me. Now they are suggesting the driver possibly having a "senile moment"? Weren't the brakes on the car fried? Even if he had both the gas and the brake pedal depressed, according to Toyota, the software would have ignored the gas pedal...

    If the problem is real, then these UA issues will continue....

Jim
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W3RSW
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« Reply #118 on: March 16, 2010, 11:09:42 AM »

Statistically, given thousands, maybe millions of lines of code, and coupling that with human interaction and 'control', one can expect glitches sufficient to cause a runaway car now and then.

...and then 'they' will take over. All will become calm and orderly. Grin
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« Reply #119 on: March 16, 2010, 11:11:31 AM »

I just saw on TV that now they suspect cosmic rays may screw up the Toyota computers.    I am almost an old driver, 66 in another month.     I get just as mad when some old fart pulls out in front of me then goes much slower than the speed limit.  I get just as mad at yuppies who tailgate me while I am usually going 5 mph over the speed limit.   I have found that you can go 5 mph over the speed limit in PA and never get stopped for speeding.    I have never been found guilty of a speeding violation.  When I am 70 things may be different.   In PA they retest old drivers, including the written exam that covers minor details of the motor vehicle code.    Many in their 80's or older just don't bother to retest and lose their licenses.
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ke7trp
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« Reply #120 on: March 16, 2010, 12:17:45 PM »

This kind of thing is really individual.

My Grandpa is 94!!!! and Drives everyday in Las vegas Traffic.
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K3ZS
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« Reply #121 on: March 16, 2010, 01:13:07 PM »

I hope I am still alive at your grandpa's age, whether or not still driving.     Some people age differently, some physically, mentally or both.    Looks like good genes run in your family.
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ke7trp
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« Reply #122 on: March 16, 2010, 01:31:35 PM »

He is a health nut and wrote many books

http://cardiofitnesshealth.com/index.htm

http://www.lifeahead.net/index.htm

Click the lifeahead program and download it. Its free.   It will tell you how long you will live Smiley

C
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W8EJO
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« Reply #123 on: February 08, 2011, 04:06:13 PM »

These congressional Toyota hearings remind me of the old Soviet Show Trials.

GM is government owned now, just like in the old USSR Gorky Automobile Factory (Volga).

The government is simply attempting to damage their competition via this show trial. 

Toyota is being singled out for its recent recall of nearly 650,000 cars. Ford recalled more than 4 million vehicles last year and was not subjected to a Congressional Hearing (UAW = big political donor).

Grow up & do the math.

Case closed!

http://www.latimes.com/business/la-fi-toyota-nasa-20110209,0,4830024.story


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Terry, W8EJO

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w3jn
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« Reply #124 on: February 08, 2011, 04:51:53 PM »

Quote
Last March, NHTSA enlisted the help of NASA engineers with expertise in computer-controlled electronic systems and electromagnetic interference after there were complaints that the agency lacked the expertise to conduct such a review.

So was this just a software and EMC review?  Not sure NASA would be the best agency to do either.
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