The canister purge solenoid valve is a container located inside the engine bay that houses fuel vapors to be recycled back into the combustion system when necessary. It is normally mounted on the firewall of the engine compartment.
The canister purge solenoid valve also serves as a diagnostics tool used to troubleshoot the emission system. The valve is able to be manually shut to test for leaks in the system.
The canister purge valve is difficult to diagnose since its failure can cause other sensors from the emission system to malfunction. When the charcoal inside the canister breaks apart, it may cause some pieces to jam the valve. Common symptoms of a malfunctioning canister purge solenoid include an erratic idle and illuminated check engine light.