Contour Enthusiasts Group Archives Forums General Troubleshooting '95 V6, memory code 172...should I be concerned?

I get a recurring but intermittent CEL with my car. The two times I've checked my codes, I come up with:

172 (R,M) Oxygen sensor not switching - system is or was lean - Single, Right or Rear HO2S

I've had the CEL come on and switch off on its own during driving, and this has been on and off for the better part of the year that I've owned the car. I don't tend to flog it...it's a V6/auto and I don't pass 5K rpm much, more from lack of opportunity than anything but still, I want this engine to stay healthy. Thoughts?

First I'd try running some Techron fuel system cleaner. If it persists, check your O2 sensors.

I had that CEL code on both my daughter's '95 V6 Contour, and my wife's 95 V6 Mystique. They occurred at 55-60K miles.

In both cases I had a shop replace the O2 sensor (bank 1, on firewall side). Apparently that O2 sensor is prone to changes over time. It seems that the CEL was due to a faulty sensor, as it did not come back (not that code, anyway).
I'm not sure what the computer does when it receives the signal from the sensor, but the computer will assume the sensor is good and make adjustments. This could affect gas mileage and driveability. The sensor was about $50 plus installation. I do know that the sensor will continue to degrade, so my recommendation is to replace it.

Thanks for the responses.