At 08:20 AM 8/3/01 -0700, you wrote:
>If the second o2 sensor went bad, would it cause my truck to run bad? Or is
>it just like a check engine light trigger? I am running out of options to
>check here =) The thing is the most handsome truck out... so i would like to
>get it running right but whatever WEs
The following is what I've read about Chrysler downstream O2 sensor.
I have nothing else to go on to confirm or not confirm it.
Chrysler OBDII vehicles do use the downstream O2 sensor input to optimize cat
converter performance. Supposedly, Chrysler has a patent on the system
in which the downstream sensor is used this way.
Since the introduction of OBDII with both upstream and downstream O2 sensors,
the downstream O2 sensor has been used to evaluate catalytic converter
operation
and to control converter efficiency.
When looking at the upstream O2 sensor goal voltage, it should fluctuate above
and below the normal center (.4 to .6 volts) based upon what the downstream O2
sensor is reading. The vehicle should be driven through all speed ranges when
checking goal voltage. If the goal stays high or low all the time, a
thorough check
of the downstream oxygen sensor should be made. Be sure to check the sensor,
wiring harness, connectors, catalytic converter itself, and inspect for
exhaust leaks.
Although a MIL lamp may not be illuminated, there are instances when the
downstream
O2 sensor goal voltage is out of range, causing driveability problems or
low fuel economy.
If the downstream O2 sensor tends to stay below center all the time, the
PCM will adjust
the goal voltage higher in an effort to correct the low O2 readings of the
downstream sensor.
This can result in low fuel mileage.
If the downstream O2 sensor has a tendency to stay above center, the PCM
will set a low
goal voltage which results in a lean fuel mix which can cause the engine to
run hotter and
aggravate a spark knock condition.
Sometimes a service technician will reset the PCM and take it for a test
drive. The PCM
does a recalibration after the reset, and the problem may go away until the
PCM has completed
a relearn of the system and then begins to attempt to correct for the
downstream sensor error.
If the symptoms reappear after several days of driving after a service is
performed, check the
downstream O2 sensor, the exhaust system, the wiring, and the catalytic
converter.
Note: a worn out catalytic converter can produce symptoms similar to a bad
downstream O2 sensor.
I had sit the above aside because it runs contrary to most of what I've
read about the downstream
O2 sensor. I know the diy-efi knowledgeable people have had debates about
what the
downstream O2 sensor affects and does not affect.
Sorry to have made the water muddier.
Bob Tom Burlington, Ont., Canada
'97 Dakota Sport, 4x2, CC, Flame red, 5.2L, auto., 3.92SG
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