Wow. Why wouldn't you just dump the firmware, nop out the limiter code, and reflash?
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Replying to @RichFelker @whitequark
because those ECUs startlingly often use pathologically arcane and proprietary microcontroller architectures.
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I thought most of them nowadays are ARM or SH?
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I'm guessing from context it was really old, not nowadays. But for an old Toyota my guess would be SH-1 or SH-2.
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do you know how they do redundancy? I know in aerospace they sometimes have a primary channel and a monitor/standby channel that does the same computations and then some stuff for switching in case of failure, but idk how they do that in automotive ECUs
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On vehicles from before the late 90s (maybe even later than that) I doubt they have any redundancy. The ECU just isn't that important. If it fails, at worst the engine stalls. It's not like modern drive-by-wire or Tesla's brilliant brake-by-wire mess.
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i guess if the throttle is controlled by a traditional Bowden cable it's not that bad (unless there's a cruise-control bowden cable as well, since the throttle opening will be max(gas pedal, cruise-control command)).
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Replying to @alt_kia @RichFelker and
(I have throttle-by-wire and it’s super endearing—when you turn the key to the “run” position when the car was off and the pedal is pushed down all the way, you can hear the sound of the throttle instantly moving to the wide-open position!)
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Now I'm actually curious how *real* fail-safe accelerator pedal would be designed in a pure electric vehicle. Probably should be some kind of resistor/fuse array routed by pedal position inline with current to the motor(s).
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Replying to @RichFelker @alt_kia and
See also: https://betterembsw.blogspot.com/2014/09/a-case-study-of-toyota-unintended.html … (The streaming video is best)
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Pretty sure they didn't have a real fail-safe... 
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Replying to @RichFelker @alt_kia and
Soooo, supposedly, the closest thing to a failsafe was that if you held down the start button for 3+ seconds it would kill the engine. That's not a fail safe, but it was an out.
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