Unintended-acceleration investigation continues

I must note that I came to the Prius from a series of manual transmissions, and still have them in the household. My SUA incident was a wrong-pedal event in a manual transmission. And despite the extreme fatigue that caused the event, it was still resolved instinctively with the clutch. The root cause was clear before the adrenalin rush subsided, so there was nothing to report.

Note that the previous studies found SUA reports very disproportionately weighted towards automatic transmissions, far more so than the difference in popularity.

The clutch reflex was not the only instinct used in my incident. Treating the 'failed' brakes as a loss of traction on ice, I pumped the 'brakes', releasing the floored gas pedal and hitting the correct pedal on the re-try, and providing more touch and feel clues about what really happened. This pre-ABS reflex worked even in the middle of summer, and would have been sufficient had the clutch not already finished the job.

But now that ABS is common, this reflex is also vanishing from much of the driving population.

 

Pushing the engine "off" PB, even if you know to hold it for 3 seconds, does NOTHING but send a signal to the engine/transaxle control ECU (microprocessor). Therefore you are relying on the proper operation of the "firmware" (software, programming) in the ECU to "notice" the PB depression and act accordingly.

Same goes for the shifter, a set of switch connections are used to send signals to the ECU indicating what/which "gear" you want the ECU to select.

Deadly-embrace and dead-lock are terms familier to the industry. Basically they both result in the firmware being stuck executing only one series of instructions thereby ignoring all other functions.

Lets say you engage the cruise control knob and hold it until you attain a certain speed. Now you release it but the switch doesn't open and the car continues to accelerate. In the above case almost anything you would do, step on the brake, etc, would correct the problem.

But what if, for instance, there is a flaw in the base micropressor design that on very rare, extremely rare, occassions causes it to get into a dead-lock mode?

I have personal experience with such a design flaw. The microprocessor that my company designed exhibited a design flaw ONLY in certain highly unique circumstances. That was when executing a multiply instruction with one of the registers/accummulators, having an all "ones" condition. The flaw was corrected by adding more ground "ties" to the substrate near the ALU internal structure.

 

"...Toyota is now adding this feature.."

Yes, but using, relying, on the very same firmware instruction execution sequencer that might have very well been at fault in the unintended acceleration instances to begin with.

 

what if meteor comes down and hits you in the head, tomorrow?

there is no such evidence that any of those issues are remotely possible. NASA investigated Toyota vehicles for 10 months trying to find any such issue.

Not to mention that car ecu's are isolated from each other, they are not home computers. If cruise control fails, it has nothing to do with transmission ecu which is different, and they all have multiple failovers.

You are basically throwing s*it on the wall, hoping something sticks. Same as that safety research group is doing (while getting paid to do so).

 

they have never found any car with functioning brakes that would not stop the car, even with throttle at WOT.

With smart brakes, it now tells ecu to put throttle to 0% as long as you have brake applied... so you cant ride the brakes anymore to the point of failure.

 

The biggest and most publicized case was the lexus driven by the police officer. The brakes were most likely worn by being used previously with pedal entrapment. The dealer, not the driver put the floor mats in the loaner car. I don't really want to rehash the facts of the case, but the remedy proposed to toyota before the incident was brake over ride, which toyota has now implemented. Many cars with unintended acceleration were stopped by use of the brakes, but in the case of entrapment or stuck gas pedals the stopping distance is greatly increased without brake over ride. The issue is at least to the nhtsa closed now. Toyota has replaced bad gas pedals. This safety feature was already in our prii. I fully support foia, but doubt there is anything there.

 

Have you tried that with a FWD, WOT, and starting at ~70MPH...?

With RWD the front brakes, the primary brakes, could probably bring the car to a stop.

But with the engine at WOT and DRIVING the front wheels AGAINST the primary brakes...not so certain.

 

I think by "primary brakes" he meant to infer that the front brakes handle around 70% of the braking duties. So while braking is applied to all 4 wheels, the fronts are responsible for the majority of the braking force.

 

The key is, car and driver did not test the cars with worn brakes. That's why they added -

They could have added many other cars like the prius to the list. Hyundai also promised to add the feature to their cars during the investigation.

 

You never know when that might happen, that's why I wear a rubber pad underneath my tinfoil hat.

 

Worn service brakes pretty much work as designed until you wear through the lining and running on the backing plates. Whether the pads are nearly new, 50% worn or 90% worn won't make much difference in braking ability.

 

I somehow doubt that was the case in the saylor case. If they started worn 70%, what happens in WOT. Lots of things had to go wrong for the tragedy. Dealer had to ignore a users complaint of UA and put the wrong floor mats in the car. The gas pedal had to get entrappeed, the driver did not or could not shift into neutral or shut the car down.

Toyota Recall Accident | New details in crash that prompted Toyota recall - Los Angeles Times

unlikely course of events, but with millions of cars on the road, bad things add up. Brake over ride seems like a better safety feature than 9 instead of 6 air bags I'm glad toyota made the change. stuck throttles happen.

Let me add that the cars have always been very safe, and it is the drivers responsibility to know how to shut them off and shift them.

 

uh, as i said, this is all very old... many magazines have tested Camry V6 at full WOT at 100mph and brakes overrode the gas.

this is why all this media hoopla went nowhere, nobody could ever replicate bad behaviour except for drivers panicking.



in any case, original story is Kane trying to milk more money from Toyota by using broken Prius that NTHSA gave up on. THis is the same guy that staged Camry brakes "malfunction" on ABC where they spliced the wires trying to make brakes not work.

 

You can read all you want about the saylor lexus and decide for yourself, either from the old link I posted above or newer ones. Brakes definitely were hit in the car, no damage to the master cylinder. Previous driver of the car had reported UA, but the car was sent back out. We can not tell how warn the brakes were before saylor got it, since the dealer did not check it out.
+1

Agree with the first part.
The worriers only get loud if there are incidents, and the changes to floor mats, gas pedals, software seem to have cut down on reports greatly.

 

Your post betrays no recognition of the differences between the architectures of PCs and real time safety critical systems. You speak as if there is only one processor running everything, creating a single point of failure. Such a design would flunk any safety review.

Real car designs have many independent microprocessors intended to keep complete failure of any one system from disabling other critical systems. Any common known throttle control system failure that could have also taken down the brake control system would have raised huge red flags in the government reviews of Toyota's electronic throttle controls.

There are multi-point failures that could be dangerous, so there is still room for improvement. But the current all-electronic systems are much better than the mechanical systems they replaced.

Not so fast. I've heard allegations of a car that, at WOT with hot brakes and the power brake booster depleted, could not be stopped at the 500 newtons (~112 pounds) of brake pedal force used in other federal brake requirements. It could be stopped at 1000 newtons, but that exceeds the strength of numerous drivers.

The Toyota SUA hysteria two years ago highlighted this problem as a hole not addressed by those federal regulations.

 

Yup....

I performed just such a test at 20mph and at 100mph in my Prius. The car stopped revving and began to slow down rather quickly but in a controllable manner. Well the 20mph test almost had me eating steering wheel.

I've also tested the other THREE methods of stopping a runaway situation (Power button, neutral shift and park button) and all three worked exactly as stated in this thread. Despite expecting the car to freak out and causing an unsafe situation, each method produced a smooth and non-obtrusive shutdown of acceleration in a very satisfactory way.

The only times could envision a problem is the car going WOT right as you are trying to navigate and intersection AND the brakes somehow fail at the exact same time. With normal functioning brakes the car will stop just as quickly whether you have your foot off the pedal or have the pedal mashed to the floor. It makes no difference.

This is a terrible video and a terrible place to perform the action but it illustrates the point.

YouTube - Broadcast Yourself.

 

Yes, like many the highlighted text is pure supposition on your part with no facts whatsoever. IOW, it's useless trash.


What has been found is that

• the AW Mat was melted onto the gas pedal; the pictures were in the NHTSA/OC Sheriff's Dept report
• the very same vehicle had the very same problem one or two days prior but that older driver had the composure to hold the brake down without releasing it and to pull over to the side where he could dislodge the AW Mat from on top of the gas pedal. When he accomplished this he returned the vehicle to the Lexus dealer with no problem at at.

IT WAS THE MAT!!!

No matter how much you might speculate otherwise it's only your personal opinion but there's no evidence to show any other cause except the mat.