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What is electronic throttle control? Whats under the hood? What is needed?

So what is this electronic throttle control system that people suspect is causing Toyotas to take off when nobody is stepping on the gas? I’ve seen a lot of technical and confusing drawings, but it really just comes down to this. It used to be that when you stepped on the gas pedal, it was attached to a cable. The cable ran to the throttle valve, and directly controlled engine acceleration. Back off on the gas pedal and the throttle closed down, reducing engine speed and the car’s speed. Pretty simple.
Today, it is not so simple. There is no steel cable running between the gas pedal and the throttle in an electronic throttle controlled vehicle. Electronic sensors figure out how far the gas pedal is depressed, convert this to an electronic signal, and send it to a mini-computer (the electronic control module.) From there, the ECM does some calculations on optimal inputs to achieve the results it understands the driver desires with the greatest fuel efficiency, and sends another electric signal to a small electric motor that sits next to that throttle, which interprets the signal from the ECM computer, and opens and closes the throttle accordingly.
As you can see, there are a lot more places for something to go wrong with the electronic throttle system than with a simple steel cable. That does not mean we should go back to the “good old days” of 1960s technology. It appears there are real advantages to this system such as improved gas mileage and durability. I have been a big advocate of technology that makes our cars safer and more fuel efficient.
My understanding is that if that steel cable ever broke, and I don’t know that it did very often, a spring would close down the throttle and return the car to idle speed. That is a very simple safeguard. It is apparently similar to the safeguard Toyota tried to program into its computer – returning the throttle to idle or reduced power if ever the electronic throttle control malfunctions. However, it appears that safeguard has not worked. Remember, it is controlled by a computer and electrical signals too.
That is why we advocate a very simple solution. If the driver steps on the brake, the throttle motor needs to shut off and return the car to idle, just as tapping the brake shuts off the cruise control.
- Stuart Ollanik

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