As I said previously, even if the engine was left idling during the ASR discussion, the catalyst will cool off enough to reduce oxidation efficiency. Note that the O2 content at idle was 0.2% percent versus 0% previously. Zero percent O2 indicates 100 percent oxidation efficiency as all the O2 is being consumed to oxidize HC and CO in the catalyst, and the emissions are very low.

During the 2500 RPM test the catalyst heats up, and efficiency is improved with only 0.1% O2 and lower emissions than at idle, and the difference between the recent and previous test is much less.

The 02 content is an important diagnostic tool. If any is left it may mean the catalyst is not operating at 100 percent efficiency, and a hotter catalyst will be more efficient. If O2 is 0.2% or less emission performance is usually within limits, and the lower the O2 reading the lower the emissions. If O2 level is 0.3% percent it might squeak by or marginally fail.

There is likely nothing wrong with your car. The catalyst was just too cold due to the excessive idle time. Keep this in mind for your next test. No long highway trips since the last test is not likely a factor.

Duke