1998 O2 sensor

[Len Sabatine]

At 01:50 PM 6/6/00 -0500, you wrote:
>If I understand right, the 98 GM trucks had 4 O2 sensors. 2 of them mount
>after the separate catalytic converters. I am looking at installing a 98
>Vortec 350 into a truck that has a single cat. Will it throw anything off to
>have both of the 98 O2 sensors mounted in the same exhaust tube after the
>single cat?
>
>Paul Washburn
>lpwcruzr at netzero.net
>
    If utilizing the 98 PCM OBD2 config , you'll need to utilize the Pre - 
Post Ho2s on each side
of the engine since the PCM is calculating Bank to Bank Fuel Trim based on 
all 4 sensors.
OBD2 is real fussy about these things, you may also need to use  the 98 
Cats since they contain
cerium in the catalyst mix. The Secondary [ Post Ho2s]  are monitoring 
after cat mixture condition
in this manner. The Heated O2s are also necessary for the PCM to go into 
closed loop in the
proper monitored time frame as is done with OBD2  , otherwise the ODB 2 
Monitor will set a flag
and most likely produce other undesirable conditions. OBD2 isn't forgiving 
if monitored sensor inputs
are out of calibration range.

  Len

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