Phase 1 - Reference Measurement
The ECM activates the pump motor. The pump pulls air from the filtered air inlet and passes it through a precise 0.5 mm (0.02") reference orifice in the pump assembly. See Fig 1.
The ECM simultaneously monitors the pump motor current flow. The motor current raises quickly and levels off (stabilizes) due to the orifice restriction. The ECM stores the stabilized amperage value in memory. The stored amperage value is the electrical equivalent of a 0.5 mm (0.02") leak.