Code P0141 help, which part? on a 4 cyl Sunfire

I'll ask here instead of the Cavalier/Sunfire threads in hopes of a better answer.

I'm getting an intermittant P0141 code, HO2S Heater Circuit Bank 1 Sensor 2, on my daughter's '97 Sunfire.

This is the heated oxygen sensor after the catalytic converter, the 4 wire unit. The light comes back on after 7-10 days after I reset the code.
So how can I tell if this is the sensor, or a plugged converter?

The part itself is $90.00, has about a 6 ft wire harness, and the connector is under the intake manifold (hard to get at- I can't quite see it), while a true fit converter is almost 3 times that.

Car runs fine, just a little bobble when first started while cold- about 10 seconds of rough fast idle. No smelly exhaust.

The code is for the sensor heater circuit.
Not a cat or sensor operation.
Check wiring and voltage to sensor heater and for good ground.
Some also have a fuse on 02 sensor heater circuit.
MT