How many oxygen sensors on 2000 Dodge Grand Caravan?

Thank you Tom. When I went to have it tested at Auto Zone, the man said it didn't say which sensor it was so he "assumed" it was bank 1 sensor 1.

over a hundred thousand replace both up an down stream sensor. will need to take off wipers whole assembly to get to the up stream behind the motor . good time to replace spark plugs back there an wires and don't forget the pvc and hose there. that assembly off not to hard need a lisle wiper removal tool works great makes it easy.

probably need both valve cover gaskets changed if over 100k in miles . I changed the front one pretty easy ,the gasket was bad worn out . use no gasket sealant on the new gasket none on the old one either . make sure its cleaned up no stuff left ,shiny metal were you put valve cover back on. will need a swivel adapter to get bolts out in two places there. back valve cover may be harder to do may need to remove upper intake. haven't done the back one yet.

Is there also 2 02 sensors on .y 2009 3.3l grand caravan SE? And what, if so, are each ones job?