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Toyota To Let People Ride In Self-Driving Prius
fergus07 writes "Toyota is to show an autonomous Prius at Tokyo Motor Show. Dubbed the Toyota AVOS (Automatic Vehicle Operation System), the car will be available for members of the public to take 'back seat' rides at the show, demonstrating first hand how the Prius can avoid obstacles, be summoned from a parking garage and park itself."
No car I'm aware of has truly redundant o2 sensors.
The sensor(s) in the exhaust manifold (front o2 sensors) are for fuel trim. A failure or insane data in one or both causes the PCM to failover to preset maps and it begins basing injector duty cycle on the value in the maps that correspond to MAF/MAP, throttle angle, engine speed, etc. A failure in both sensors (assuming two banks) doesn't render the car undriveable.
It depends on vehicle manufacturer how a PCM handles a reasonbly responding sensor in one bank and a failed/insane sensor in the other. It may start using the values from the good bank to control how it fuels the failed bank OR simply go to the maps for both banks.
The rear o2 sensors ie., behind the catalytic converters, are used to determine if the catalytic converter is functioning properly. Failure or insane values from those sensors will trigger a check engine light and may (sometimes) cause the computer to go into a limp home mode. This is ostensibly to prevent some kind of engine damage, but my guess it's really a deterrent to basic tampering-gutting/removing of the catalytic converter, or to push the owner to repair a damaged/clogged converter.
Their position behind the catalytic converter renders them pretty useless in deciding fuel trim.