Greetings from Finland.
I have Stratus from '96 with 2.5L V6 engine.
It has been running for 212 000 km but is now displaying error message.
According to dealer it is Front bank upstream 02S stays at centre.
By "igniton key"method I have code 21 which says that sensor voltage to computer not fluctuating.
So I think it is the sensor on exhaust side before cat,am I right?
I checked the connector,it looks ok.
On connector I have four wires,green/orange?(or red),black/blue?(or turquese),brown/white and black.
Has anybody experience how does that sensor work?Should I have steady +12 volt on one of the wires from battery,
now only wire that has something going on is green/orange.
When engine is running voltage from 7.8 to 13.5 volts appears on that wire.
at same time idling speed is varying.
Is it really the sensor that is gone or has someone had similar problems being finally something else?
Haynes book does not have diagram for sensor connections:=(
I hate this cause engine might run ok for some period and then lights up the check engine...

 

just get yourself a new o2 sensor, and slap it in...shouldn't cost much...