Catalyst Efficiency % and Volumetric Efficiency are two tests made quicker and easier with the ATS EScan. In this article Jerry Truglia uses both to simplify the analysis of a P0420 on a Toyota Prius and detect a driveability problem on a 2005 Subaru Forester. 

The Prius: when running a Cat Eff test, the GREEN indicates the cat's capability of reduction and oxidation is good. The screen below shows the test being run at idle with 96 cat eff %.

When the value for Catalyst Efficiency % changes to RED this indicates a problem with the cat. In this case the Prius showed GREEN cat at idle and 1500 RPM but at 2000 it turned RED with 53 cat eff %.

The 2005 Subaru Forester: a test of the Mass Air Flow (MAF) sensor using the ATS EScan uncovered the problem...

The frequency on the yellow graph indicates a clog in the exhaust system such as a clogged catalytic converter. Using this test saves time since we do not have to remove any AF or O2 sensors and perform a back pressure test.

Read the complete article by Jerry Truglia at: http://www.searchautoparts.com/automechanika-chicago/commitment-training/exploring-variety-challenges-asian-models