Operating Diagram

When diagnosing leakage, the ELCM closes the COV, operates the vacuum pump, measures the pressure at a point past the orifice, and then sets this pressure as the reference pressure. Then, it opens the COV and operates the vacuum pump to measure the pressure of the fuel system. Since the reference pressure is identical to the pressure when there is leakage in the fuel system, the ELCM compares the reference pressure with the fuel system pressure and determines that leakage has occurred if the latter is higher than the former.

Courtesy of KIA MOTORS AMERICA, INC.

Measure the reference pressure	Measure the system pressure
Courtesy of KIA MOTORS AMERICA, INC.	Courtesy of KIA MOTORS AMERICA, INC.
Measure the pressure past the orifice by operating the vacuum pump	Measure the pressure of canister by operating the vacuum pump and COV valve