Function Test

Leak diagnostic is divided into different phases. Each component is tested before actual leak diagnostic begins. Leak diagnostic is cancelled if a DTC is stored due to a faulty leak diagnostic system component during any phase of function test. Leak diagnostic test works as follows:

• Leak diagnostic system must depressurize. ECM ensures that pump diaphragm is in resting position. DTC ECM-65, Faulty Signal, is stored of ECM determines that pump diaphragm is in active position during this phase.
• When engine is started, intake manifold vacuum is created. Three-way valve opens and vacuum moves into non-return valve. Leak diagnostic pump diaphragm is moved into active position by vacuum. P0450/ECM-65: Evap Leak Diagnostic (High Signal), is stored if ECM determines that pump diaphragm is in resting position during this phase.
• Three-way valve and non-return valve close. Atmospheric pressure is vented into leak diagnostic pump and diaphragm returns to resting position. P0450/ECM-65: Evap Leak Diagnostic (Low Signal), is stored if ECM determines that diaphragm does not return to resting position during this phase.