O2 sensor troubleshooting 1998 Caravan

1998 Caravan 3.0L
replaced downstream o2 sensor about three months ago
check engine light went off-good
replaced upstream o2 sensor last week
check engine light came back on saying downstream o2 sensor faulty???

Anyone now if this could be something else. I don't think I should
have to replace o2 sensor after only three months.
Is this really going to effect anything if I drive with light on. I
don't have the time or money to deal with this kind of crap. Nobody
has been able to offer an answer on this so far.
What about disconnecting completely? Could this harm the engine in any
way? How much could it actually effect gas mileage?

Thank in advance.
K

 

My guess is that you replaced them with Bosch sensors. Bosch sensors do
not work well on some (many? all?) Chrysler products. Daniel Stern used
to say this, and I was skeptical, but I have seen thread after thread
after thread on the various LH car forums by people who learned the hard
way attesting to the fact that it is true. Get them from the dealer.
Also NGK's work well (I think for some years they are the OEM sensor).

 

what kind of o2 sensors did you use??
a good scan tool tool is the quickest way to look at operating voltages
but a d.v.o.m will work but takes more time to hook up
i can only hope you used chrysler parts and not autozone crap

 

Must be a new trouble code. I've never seen a code that says an O2
sensor is faulty.

The answer is it needs to be properly diagnosed.

Can't help with the money, but, if you used the time you've spent
whining about it and throwing parts at it, on actually diagnosing it
instead, you'd be better off.

Disconnecting it will guarantee the light will always be on. Then
you'll never know if something worse has developed.

In addition to monitoring cat condition, the downstream O2 is also
used as an input by the PCM to determine upstream O2 goal voltage.
Fuel mileage may be a concern, but I'd be more concerned about what
would happen to the cat if it ended up running too lean.