P0420 - back after winter

I have an '01 with 189k miles. I have only driven it for about 6k miles. It has the intermittent check engine light - which is a p0420 catalytic converter code.

The funny thing is that the check engine light was off the entire winter. Now it is back on.

I'm not sure of the correlation, and I haven't been driving it any different. And I am using the same fuel.

I am planning to try to get some information using a diagnostic scanner. Then possibly replacing the front oxygen sensor.

Any ideas about the light being off all winter?

Thanks,
Steve H.

 

As far as the commute, it really varies. So all winter I was doing a variety of distances - from going to town (7 minutes) to job sites (45 min). The blue (cold) temp indicator always seems to go off after about 5 minutes of driving. Also, this winter has been quite mild compared to last, and therefore outdoor temps not super cold.

The check engine light had been on and off all last spring/summer/fall. It just happened to go off about a week before I needed an emission test in the late fall.

I am not sure if the stations have changed to non-winter fuel mixtures, or even how much that changes how it burns.

I do have a scanner that shows the voltage to the front and rear O2 sensors. I will take the car for a longer drive and take note of the readings.

Thanks,
Steve H.

 

Today I drove the car for about 20 minutes. Then, I connected my Innova ScanTool to "watch" the O2 sensor data that it shows (Volts). I went for a 10 minute drive in town, speeds of 25-45mph.

The front sensor fluctuates irregularly from .050 up to approximately .850 and back.

The rear sensor tends to hover between .750 and .830 (V). It was also dropping to .1 or so, just did not seem to do it as frequently as the front sensor.

I am not sure of the output range that it should be, but this seems like it is working correctly. Unless of course the numbers are way off.

Any thoughts about these readings?

Thanks,
Steve H.