Grand Caravan O2 Sensor Replacement

This is probably a dumb question but I have some confusion about the O2 sensors on my 2002 Grand Caravan. The books and articles I have read say that since the early 1990's there are four O2 sensors for V6
engines. One for each Bank before the catalytic converter and one after.
In searching for the sensor, I can only find two. Doidge has cleverly placed the one I can find before the catalytic converter between the engine and the firewall in order to make it as difficult as possible to get to. I did read an article saying that there is one in the crossovedr pipe. Unfortunately the front exhaust manifold and the crossover are covered with a shield and I can't see much without removing it.
Can someone tell me for certain how many O2 sensors there are and are they located between the firewall and engine and at the catalytic converter.
Thanks Dick Finn
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This vehicle has 2 sensors, an upstream sensor called 1/1 and a downstream 02 sensor called 1/2.
Glenn Beasley Chrysler Tech
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