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