Evaporative Emissions System: Testing and Inspection

Fig. 1 EVAP Installation:

Fig. 1 EVAP System Overview Schematic:

Monitoring Procedure
This diagnostic operates during the first long duration hot idle period after engine start. the diagnostic works by gradually opening the purge valve on each bank in turn and monitoring changes in AFR closed loop control value, idle speed control feedback and engine RPM. If none of these variables changes by more than a predetermined value the purge flow failure is made.

The purge valve drive circuits monitored during driving operation; if the driver state does not match the command state for over a predetermined number of on / off operations then a failure judgement is made.

Evaporative Emissions System: Testing and Inspection

Fig. 1 EVAP Installation:

Fig. 1 EVAP System Overview Schematic:

Fig. 1 ECM Interface:

Purge Valves: