I've had a CEL for the last 2 months or so, it goes away for a couple of days and then comes back, but it's gotten worse and now it's pretty much always on. I can clear it and it comes back within a day or so. It's a P1131 which my scanner says is "O2 Sensor Circuit Low Voltage Bank 1, Sensor 1".

I also notice a sulfur smell after driving a while, particularly up a long steep hill (which I do every day) - is this due to the computer ignoring the bad O2 sensor and running a pre-computed value (presumably a too-rich value)?

Should I just go ahead and replace the sensor or is there something else it might be? And which sensor is B1,S1 - the one at the front of the engine near the radiator, or the rear (there's only 2 O2 sensors on the V6, right)?

Thanks for any info

joel
'96 Contour SE ATX
Metallic champagne
Replaced headend radio
Added 6-cd changer
Standard high-beam bulbs used in the low-beam lights
ATX rebuilt at 102K
Otherwise stock.