Catalyst Test Time Difference EWMA

The display shows seconds from - 25.6 to + 25.5. This display indicates the Oxygen Storage content of the exhaust catalyst. With a properly operating exhaust catalyst the Catalyst Test Time Difference EWMA should always be less than the Catalyst Test Fail Threshold. Although comparing this display to the Catalyst Test Fail Threshold may aid in determining if a catalyst is failing always allow the idle catalyst test (DTC P0420) to Pass or Fail a catalytic converter.