Hmmm...from the Service Manual, p. 14-41, 42:
UPSTREAM OXYGEN SENSOR
The input from the upstream heated oxygen sensor
tells the PCM the oxygen content of the exhaust gas.
Based on this input, the PCM fine tunes the air-fuel
ratio by adjusting injector pulse width.
The sensor input switches from 0 to 1 volt, depending
upon the oxygen content of the exhaust gas in
the exhaust manifold (this is offset by 2.5 voltage on
NGC vehicles). When a large amount of oxygen is
present (caused by a lean air-fuel mixture), the sensor
produces voltage as low as 0.1 volt. When there is
a lesser amount of oxygen present (rich air-fuel mixture)
the sensor produces a voltage as high as 1.0
volt. By monitoring the oxygen content and converting
it to electrical voltage, the sensor acts as a rich-lean
switch.
DOWNSTREAM OXYGEN SENSOR
The downstream heated oxygen sensor input is
used to detect catalytic convertor deterioration. As
the convertor deteriorates, the input from the downstream
sensor begins to match the upstream sensor
input except for a slight time delay. By comparing
the downstream heated oxygen sensor input to the
input from the upstream sensor, the PCM calculates
catalytic convertor efficiency. Also used to establish
the upstream O2 goal voltage (switching point).
So...will horking these two inputs confuse the PCM and mess up the injector pulse widths?
Deleting the cat: O2 sensor outputs match, thinks A/F is rich, thinks cat is dead, triggers CEL
Deleting the cat, let downstream O2 sensor dangle: thinks A/F is terribly lean, dumps fuel to match, ???
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