On Thu, 26 Nov 2009 23:42:03 -0800, "Bill Noble"
wrote:



"Bruce L. Bergman" wrote in message
.. .
On Wed, 25 Nov 2009 23:26:09 -0800, "Bill Noble"

snip ----

They need a brake pressure sensor input goiing to the computer - if
the brake pedal pressure is are over 25 lbs., ignore the throttle.
They want to stop.

RULE: Conflicting control inputs should invoke a Fail Safe.

Replacing the floormats and modifying the gas pedal is a classic Red
Herring. The problem is deeper, and allowing them to Mesmerize you
with a fake fix isn't helping anything.

-- Bruce --

agree - there is both denial at Toyota, and a lack of safety concern - when
I designed safety critical systems that had software, I always assumed as
part of the design that the software would do whatever the worst thing was
(or worse things) and then made sure that there was a way to make the system
safe even when the software did that stuff. Your examples are what I would
call a "reasonableness check" - I also agree that all vehicles should have
at least 3 positive ways of removing power from the drive train - in a
manual transmission, the clutch does the trick, as does the shift lever, and
a traditional ignition switch. an automatic would require a kill switch,
fuel cutoff or other means. Since most cars have an electric fuel pump,
stopping the pump will stop the car in short order so that is a possibility.
If I had one of the affected Toyotas, or anything with a lot of software
control, I'd add a manual switch that could interrupt power to the fuel pump
or to the engine computer - either one will work, though the fuel pump will
probably be easier and less likely to cause side effects.

Just have to be careful what you cut, and how. You don't want to
damage things in the shudown or start throwing diagnostic codes, so
cutting the fuel pump power is probably safest. Or if you want a
mechanical backup, pull a knob and a cable operated valve shuts off a
ball valve on the fuel line.

On a diesel, the good old fashioned manual air damper works - pull a
lever, cable linkage drops a cork into the air cleaner snout. Very
useful on an engine that has sprung a leak and is ingesting it's own
motor oil and running away.

(Happens often enough to mention on the horizontal Detroits on mid-
engine Crown Coaches. Other than that, the darned things will live
just about forever if you keep fresh oil and grease in them. )

-- Bruce --