Oxygen Sensor Failing???

Anyone know what, if any, are the symptoms of an oxygen sensor failing??

When i am driving with the window down i can smell fuel (i think..could be exhaust) and was wondering if it could be the O2 sensor. My cat converter is rattling and a dude at a garage said that often faulty O2 sensors dump too much fuel and destroy the cat.

Could this smell be from the O2 Sensor??

Thanks

95XJ Sport
AX15
130K KM

He's right. I've had both a 93 VW Eurovan and a 96 XJ that had their cats brun u and rattle from running rich because of o2 sensors. Replacement cats come with a warning/statment that the original cat should not have gone bad and unless the cause is corrected the new one will fail also.

JoBo

Does this cause a smell of fuel though??