Re: Oxygen Sensors when to change??

"maxpower" <damnnickname@[EMAIL PROTECTED]
> wrote in message 
news:sLOdncFZnuF-jB3anZ2dnUVZ_oGjnZ2d@[EMAIL PROTECTED]
>
>
> Not true. The first purpose of the downstream 02 sensor is to  measure
cat
> efficiency. The second function  is downstream fuel control. This
function
> adjusts the upstream 02  goal  voltage within the range of operation of 
> the
> upstream sensor. The upstream goal voltage is used to ensure long cat
life
> by allowing the pcm to control the amount of air and fuel that is
supplied
> to the cat. If the downstream 02 sensor switch point is at a  low
voltage
> the Pcm will adjust the upstream 02 goal voltage to reduce  high 02 
> content
> by . If the downstream 02 sensor  switch points stays  high, the 
upstream
> 02 sensor goal  voltage will change and  allow a low 02 content.
>
> Glenn Beasley
> Chrysler Tech

I don't get it.  There are two downstream sensors are there not?  Does the

downstream sensor on the drivers side control the bank 1 sensor on the 
exhaust manifold and the passenger side sesnor talk to the bank 2 sensor
on 
the manifold?  Is there a map as to how these sensors talk to each other. 
One of them are giving me a low voltage error thants all I know.  All cars
I 
had before now I would change the sensors at 100 K km (60 000 mile
odometer) 
read.

I got to take this car intot he delaer for a 100 K km tune-up.    Should i

be spending the $200 required to change all 4 sensors?   is this a normal 
thing?  What does low voltage from an O2 sensor mea?  What is upstream and

what is downstream?

Thanks for all the help and have a great weekend!