On Mon, 01 Mar 2010 17:55:24 -0500, email@example.com wrote:
Would need to be a compound fault, as the rev limiter has no
connection to the throttle. It shuts off injectors.
SO - even if the "unintended accelleration" problem IS a computer
glitch, it would still not blow up if put in neutral.......
And how is he "throwing it into runaway accelleration"??????
My question too!!!!!! Is it on you tube? I saw the one where a
professor basically shorted two wires and the car went into runaway
mode. The brakes could not stop the car but putting it into neutral
then using the brakes worked. I question the odds of that same short
circuit happening, but I saw that on the code reader it showed no errors
after its runaway test.
That was his big point. Gilbert is his name. that it didn't set a
code, when Toyota insisted it would.
His other point was that shorting two wires made it accelerate. That
might have been a lesser point, because I don't know if in practice
those two particular wires could short. But he wasn't claiming to
have found the actual problem, just showing that he could have runaway
acc. with no code.
As long as the inputs used are not outside normal limits, and the
results (output) are what the inputs are calling for, why WOULD it set
If the input he shorted resulted in an input voltage that WAS supposed
to result in full throttle accelleration, it would not detect an
IF however, some stray input (RF or whatever) got into the mix and
caused the engine to rev higher than the inputs would indicate (which
is what so many who know nothing about how digital full authority
engine controls (aka FADEC) works are postulating) the computer WOULD
trip a code in all likelihood.
I don't know. But it proves false Toyotas contention that there were
no problems with the electronics- 'because if there was an electrical
problem a code would be set.'
Stray input, short, open- all possible. Apparently one of those was
able to cause the problem without leaving a code.
Toyota should have known that it was possible as at least one customer
got his racing engine to the dealer where the service tech observed
it-- and was not able to pull a code.
Simply because I happen to think (as, apparently, did at least _one_
driver) there might be an alternative to simply hanging on for the ride
that one behind the wheel might take???
Interesting definition, that... :)
If it was an "electronic problem" it would set a code. If it is a
mechanical [problem it won't set a code (usually).
If someone gets inside the computer and starts fooling around, it is
quite possible he could get tit to accellerate without showing a code
because he is "faking" a legitimate signal - which is extremely
unlikely to happen by itself in the real world.
I'm not saying it is impossible - but it would be extremely unlikely -
and certainly not common ( occurring on many different vehicles under
different conditions in different areas)
I've never claimed to know anything about the computer under my hood.
Are you saying that if a couple wires were abraded & shorted to the
frame for a millisecond that wouldn't leave a code? And that is
acceptable? [is that a mechanical or electronic problem? or do the
mechanics say electronic and the electrical engineers say mechanical?]
Who knows what the professor actually did-- but on camera he completed
a circuit and the car took off- pulled the wire & the engine went back
to normal. no code.
No chance that the right 2 wires in that harness, when connected,
could cause the fault?
I would say that whatever the cause- it *is* unlikely- because
considering the number of those cars out there, a lot of them have had
no problems. But I think there is a problem.
That's not what I said - but if, in fact, the wires that happened to
short could LEGITIMATELY have a ground potential under normal
operating conditions, a code may not be set. (actually, in all
likelihood WOULD not be set).
And yes, that would be a "mechanical" problem - although in the
electrical system. I would not call it an "electronic" problem.
However, there are very few input signals that would ever have a
ground potential. Most inputs are variable voltage between roughly one
and five volts. 5 volts is the reference voltage that the signals work
from, and the "legitimate" signal is usually something between, say
1/2 and 4 1/2 volts. I do not have the ACTUAL accurate voltage ranges
at hand - but that is the basic principal. If the input voltage to the
computer is outside the normal range, a fault is recorded and a code
can be set.
The computer can also "predict" what a reading should be in some
cases, and compare the actual reading to what it expects and cause a
code if it is wrong.
O2 sensors are a different type of signal in that they are not
resistance based, but are a voltage source. However the same basics
still apply. An O2 sensor is supposed to "clock" from roughly 0 to 1.1
volts. The higher the voltage, the richer the exhaust(less oxygen) ,
with a chemically correct mixture being roughly 0.45 volts. A standard
narrow band sensor has a steep "knee" to the signal so is not terribly
accurate, but can tell if it is too rich, or too lean, and the
computer bounces the mixture from rich to lean around that point. Just
happens the catalytic converter likes that, as it alternately absorbs
oxygen and oxydizes carbon (oxidation/reduction catalyst)
This is one place the "prediction" comes in. The front O2 sensor sees
a varying voltage, and the rear sensor is supposed to see less
variation. If it sees the right reduction in swing it knows the
catalyst is working. If it sees too much swing, it knows it is not
The computer also knows how many "counts" or crossings to expect under
given conditions, and knows there is a problem with the sensor when
the number of counts per unit time is too low, or if the voltage swing
is too small so it can set an O2 sensor failure code.
All this to say that the system of "fault codes" is NOT perfect and is
not designed to cover every possible eventuality.
It is really designed to predict emission control ineffectiveness more
than anything else, and to give someone with some understanding of the
system a place to start in troubleshooting what is a very complex
control and feedback system.
And the computer can NOT, at this point, diagnose itself.
3 computers are required to do this, with all three having an even
"vote". If two agree, and one dissagrees, it is assumed the
dissagreeing computer is at fault.
A simple "dual redundant"ystem is not fail-safe.
VERY easy to do. Simply apply a "full throttle" signal to the
fly-by-wire throttle input, or cause the cruise control "accellerate"
input to be "active". Both could be legitimate inputs, with full
throttle (or at least opening throttle) being a legitimate output.
Now, if that input were to be asserted with the transmission in
neutral, the computer would attempt to limit the RPM to protect the
engine. If the open throttle signal, in gear, did not create an
increase in speed on the vehicle speed sensor (VSS) and DID create a
difference in speed from the crankshaft and/or camshaft sensors
(engine tach signal) he computer could also throw a code to say the
transmission or torque converter had a problem.
The computer reads both the crankshaft speed and the transmission
input speed so it can tell if the lockup torque converter is working
Extremely slim chance that any 2 wires in the harness, if connected
together, would cause the problem without a code, and an even smaller
chance that they would be next to each other in the harness, AND be
subject to damage under "normal useage", if at all.
IF there is a problem electronically it is likely to be one of 3
A faulty sensor
A faulty component in the computer
A "bug" in the code.
A "bug" would generally be universal - meaning it would occurr in
virtually all of a given model/option because the firmware is "common"
to all of a type.
A faulty component OR a faulty sensor would be more likely - but you
would expect them to become "predictable" because failures usually
get worse very quickly, like an avalanche, when they start - and are
usually somewhat temperature related.
To this point there does not appear to be any kind of a pattern that
would point towards anything with any degree of certainty.
I used to do a LOT of system troubleshooting during my years as an
automotive technician - and now do a fair amount in the computer
field. (as well as some more basic electronic repairs - fixed 2 GPS
units last weekend, and 2 inoperative handheld aviation radios
On Mon, 01 Mar 2010 20:01:21 -0500, firstname.lastname@example.org wrote:
If the computer is malfunctioning, then I think you can allow for the
possiblity that it may not do what you expect on many fronts. We don't
know the nature of what is causing the fault. Is it an unreliable
oscillator? A bad ground? Leaky capacitor? Power fluctuations?
Electrical noise? Any of those things could have widepread
repercussions in the computer.
I don't know the specifics. He has equipment connected to points in
the computer that allow him to manipulate it.
I guess by applying hi or low logic signals to various circuits.
On Tue, 02 Mar 2010 08:08:52 -0500, email@example.com wrote:
Anything that stops the clock would, by necessity, stop the engine
because the clock is required to fire the injectors and time the
spark. Absolutely IMPOSSIBLE for the engine to run if the oscillator
(clock) of the ECU was to fail.
Pretty much the same with a bad ground - as the injectors are ALL
powered externally and grounded through the ECU. Also, all the sensors
go to higher voltage as the input increases. A ground (Other than the
wired signal ground for each 3 wire resistance type sensor) is not
required on the majority of sensors, and if that ground went bad the
reference voltage would go out of spec, throwing a code or the sensor
would be detected as an open circuit (also an out of range value),
throwing a different code.
About the only thing external that could be causing an accelleration
problem would be digital noise entering the system as RFI that just
happened to be exactly the right frequency and amplitude , at exactly
the right place, to fool the computer into thinking it was a
Extremely unlikely - not at all like the analogue type fuel injection
computers used on the oldD-Jetronic system like the VW412. (and EFI
I would simply assure myself that I could tell the difference between
the brake and accelerator pedals. This is the same fucking hysteria
that struct audi ten years ago. The reports vanished when audi
installed an interlock so that the driver had to have his boot on the
brake pedal before putting the car in gear.
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