RW> Yes, it has 4, two before the cat and two after. Dual Exhaust, you know.
RW> We found that one of the after cat sensors was the one signaling the
RW> computer to err, but it checked out as good in up close testing.

My daughter's old car had a similar issue with the O2 sensor after the cat. 
In her case, however, the cat was probably not functioning as good as it
should have.  

To save spending a fortune on a new cat, I bought offsets for the O2 sensor
after the cat.  That allows it to still get a reading, but not as much as
being directly in the flow.  They are used for people that remove their cats,
but don't want a check engine code up all the time.  :)

RW> Be sure you check which engine the later models have. The 97 still had
RW> the 5.7L, while the 99 could have either the 5.7L or the new for 99, 5.3L
RW> LS engine. GM got pretty close to perfection on the 97-98 fuel injection,
RW> then switched to the new design in 99 and full on LS engines after that.
RW> My high school buddy in Illinois bought a 2007 Tahoe and it came with the
RW> smaller size 4.8L LS, the same one that's in my 02 Silverado. He tows a
RW> boat and trailer and was disappointed that it downshifted to 3rd on
RW> hills.

In this particular case, it was the 5.7L.  They have both a 97' and 99' at the
local auction and they are still there.  $1900 for the 97' and $2100 for the
99'.  I was tempted on the 99', but the A/C wasn't functioning.  Everything
else checked out.

RW> All Girls Garage pointed out that the Toyota Tundras have the same
RW> problem. They blamed the blower motor speed resistor, which is probably
RW> your Durango's problem too.

Yes, it is a very common problem with them.  Last time I went to a junk yard
just looking for a few items, you could see where the Durangos and Dakotas had
their resisters, wire harness, and blowers stripped already.  I had finally
located one way in the back that still had the wire harness, which I cut out
to remove and installed in our Durango.  The old one had melted and fused
together really bad, enough to short wires.

- Mark

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