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Message: <blockquote data-quote="99Sierra2500" data-source="post: 29172" data-attributes="member: 12343"><a href="https://charm.li/Chevrolet/2003/C%201500%20Suburban%202WD%20V8-5.3L%20VIN%20T/Repair%20and%20Diagnosis/A%20L%20L%20%20Diagnostic%20Trouble%20Codes%20%28%20DTC%20%29/Testing%20and%20Inspection/P%20Code%20Charts/P0446/" target="_blank">P0446</a>SYSTEM DESCRIPTION    This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid Open and the EVAP canister vent solenoid Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid Closed and the EVAP canister vent solenoid Open. The control module monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, this DTC sets.</blockquote>