Hi Bruce,
Auto ECU's use the sensors to control fuel according to the voltage supplied
by them. Most sensors output 1 to 5 volts. More volts is more fuel. The new
drive by wire open the throttle according to the throttle position sensor.
That is also trimmed by the traction and ESC controls built into the software.
The O2 sensors are different in that they only operate on .1 to .9 volts.
They generate this voltage in response to the O2 in the exhaust. The ECM is
trying to maintain an A/F ratio of 14.7 to 1. This coincides with a voltage of
0.5. Diagnostics have an output of cross counts which is the number of times
per second this voltage crosses the 0.5V's. A high number (cross counts) is
desireable for emission controls. As with other sensors, more fuel translates
to higher voltage. The ECU then shortens the pulse width, (gives less fuel) to
respond to the excess fuel in the exhaust. An O2 sensor that has low cross
counts is due to be replaced. Fuel economy will likely be improved. O2 sensors
SHOULD not have anything to do with the throttle position stepper motor. As
with any man made device, anything can and probably will go wrong.
A few years ago, Audi had a lot of trouble with the UNINTENDED ACCELERATION
PHENOMENOM. One of the car magazines did some reasrch and found the fault to
be small close pedals that low time (new owners) mistook the gas pedal for the
brake pedal. In each incident the owners were positive they were stepping on
the brake. The magazine testers were the same as the new owners that had their
car take off. ALL CARS ARE DESIGNED WITH BRAKES THAT CAN HOLD THE CAR BACK.
Modified vehicles MAY be an exception.
In the expert witness case, the driver could not have had their foot on the
brake pedal firmly when they put the vehicle in reverse. If it had been so the
vehicle may have moved slightly, but not enough to kill anyone. IMHO.

Dale Davies