ThrottleGate Class action suits begin...
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Joined: Mar 2005
Posts: 3,123
From: Melbourne, Australia
In regards to the failsafe part of the ETC... this is my understanding of the way the systems work...
Some manufacturers specify 2 throttle position sensors, others 3. Each system employs an actual throttle position sensor, at least one of the other sensors are redundant (failsafe part(s)). - this means the 3 sensor system has two redundant sensors. I'm assuming Toyota have a 2-sensor system though this has yet to be publicly confirmed.
The 3-sensor system reads input from essentially 3 voltage curves: If the first redundant sensor agrees with the actual throttle position sensor (in this instance you essentially have two voltage curves reading the same input), it still needs input from the second redundant sensor. If voltage curve of the first two sensors increases while the other (second redundant sensor) decreases in proportion then the system believes everything is in order. If the second redundant senor doesn't decrease proportionately (i.e. if the two curves don't agree) then the ETC is disabled while still giving the driver the capability to limp home.
On the 2-sensor system, if the redundant position sensor agrees with the actual position sensor then the system believes everything is in order. There is no 3rd sensor to read (double check) from. This is where I'm curious to know if the problem relates to there not being the 3rd (redundant) sensor? If that is the case, then I don't know if Toyota can provide a solution with a software fix alone unless the brakes can be made to override the throttle and/or the engine can be made to switch off.
It's obvious that there is no override actually occurring from the fatalities that have resulted. I wonder if there is a sporadic glitch somewhere that forces the two sensor system to behave erratically which would be harder to force on a 3 sensor system?
Some manufacturers specify 2 throttle position sensors, others 3. Each system employs an actual throttle position sensor, at least one of the other sensors are redundant (failsafe part(s)). - this means the 3 sensor system has two redundant sensors. I'm assuming Toyota have a 2-sensor system though this has yet to be publicly confirmed.
The 3-sensor system reads input from essentially 3 voltage curves: If the first redundant sensor agrees with the actual throttle position sensor (in this instance you essentially have two voltage curves reading the same input), it still needs input from the second redundant sensor. If voltage curve of the first two sensors increases while the other (second redundant sensor) decreases in proportion then the system believes everything is in order. If the second redundant senor doesn't decrease proportionately (i.e. if the two curves don't agree) then the ETC is disabled while still giving the driver the capability to limp home.
On the 2-sensor system, if the redundant position sensor agrees with the actual position sensor then the system believes everything is in order. There is no 3rd sensor to read (double check) from. This is where I'm curious to know if the problem relates to there not being the 3rd (redundant) sensor? If that is the case, then I don't know if Toyota can provide a solution with a software fix alone unless the brakes can be made to override the throttle and/or the engine can be made to switch off.
It's obvious that there is no override actually occurring from the fatalities that have resulted. I wonder if there is a sporadic glitch somewhere that forces the two sensor system to behave erratically which would be harder to force on a 3 sensor system?
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