Where are the 4 O2 sensors in a 3.9L Dodge V6?

A 3.9L Dodge V6 engine typically only has two oxygen sensors, not four. They are located in the exhaust system, one before and one after the catalytic converter. The exact location varies slightly depending on the year and specific model, but they're generally:

* Upstream (before the catalytic converter): Located in the exhaust manifold or close to it.

* Downstream (after the catalytic converter): Located in the exhaust pipe further downstream from the catalytic converter.

There are no sensors on a 3.9L V6 in the usual locations for a four-sensor setup. A four-sensor setup is more common on V8 engines or newer, more sophisticated V6 designs.