Fault Criteria, Emission Related Misfiring

Misfiring could be due to exhaust emissions exceeding permissible levels.
The number of misfires causing illegal exhaust emissions depends to a certain extent on engine load and speed.
An engine load and speed dependent matrix in the engine control module's memory specifies how many misfires per 1,000 engine revolutions are needed for exhaust emissions to reach an illegal level.
When the conditions for diagnosis are fulfilled, the combustion signals from the ignition discharge module are evaluated. The fault criteria are satisfied when the number of misfires per 1000 engine revolutions exceeds the matrix value.

Conditions For Diagnosis
^ Engine running
^ Ignition timing synchronized
^ No fuel shut-of