Drivers side (left).
Bank 1, on a 4.3 L engine would be on the drivers side.
System too rich bank 1
Need more info, is this the 4 cylinder or 6 cylinder engine and which sensor on bank 1.
That would be the O2 sensor after the catalytic converter.
That should be the sensor located after the catalytic converter.
Bank 1 catalyst efficiency failure. The catalytic converter has failed.
That should be the O2 sensor just before the catalytic converter.
Bank 1 sensor 3 would be the O2 sensor after the catalytic converter.
Assuming this is a V-6, bank 1 sensor 1 would be the first O2 sensor in the exhaust on the drivers side of the engine.
System to lean, bank 1. Check for vacuum leaks under the hood.
Passenger side exhaust pipe directly after the exhaust manifold.
Assuming this is a 4.3L engine, bank 2 sensor 1 would be located in the exhaust pipe immediately following the passenger side exhaust manifold.