GM 20952523 Solenoid Assembly, Evap Emission Canister

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The PCM opens the canister purge solenoid when suitable conditions exist, such as when the engine is warmed up, the vehicle is at speed, or there's a moderate to heavy load on the engine. This allows fuel vapors to be drawn from the canister into the intake manifold for combustion.

The Evaporative Emissions Control (EVAP) system is designed to prevent the escape of fuel system vapors containing unburned hydrocarbons into the atmosphere. Fuel vapors trapped in the fuel tank expand on warm days until they reach a specific pressure threshold. At this point, the fuel vapors are directed from the fuel tank through the fuel vapor vent valve and the fuel vapor control valve to the EVAP canister, where they are temporarily stored until they can be consumed by the engine during normal operation. When conditions are suitable, such as when the engine is warmed up, the vehicle is at speed, or there's a moderate to heavy load on the engine, the Powertrain Control Module (PCM) opens the canister purge solenoid. This allows fuel vapors to be drawn from the canister into the intake manifold, where they mix with the air/fuel mixture before being used in the combustion chambers. The EVAP system consists of various components, including the EVAP canister located atop the fuel tank, which contains activated charcoal for vapor storage, the fuel tank pressure sensor on top of the fuel pump/fuel level sending unit module, and the EVAP canister vent solenoid situated behind the left rear wheel well fender liner, normally open but sealing off the EVAP system for inspections and maintenance. The EVAP canister purge solenoid, under PCM control, regulates vapor flow from the canister to the intake manifold, with its duty cycle determined by the PCM based on factors like intake manifold vacuum and sensor data. Troubleshooting the EVAP system requires specialized tools and training. Common symptoms of EVAP issues include fuel odors, particularly on hot days, often caused by loose or damaged EVAP hose connections. Checking for excessive fuel vapor pressure in the fuel tank involves removing the gas cap and listening for pressure release, while a full evaluation requires professional diagnostics. For component replacement, the EVAP canister purge solenoid on V6 engines is located at the left front of the intake manifold and requires disconnecting electrical connections, lines, and a mounting bolt for removal and reinstallation. On V8 engines, the EVAP canister purge valve sits on top of the rear intake manifold part, necessitating the removal of an engine cover, disconnecting the electrical connector, and lines for removal and installation. The EVAP canister vent solenoid, located behind the left rear wheel well, can be accessed by raising and securing the vehicle, disconnecting the electrical connector and hoses, and sliding the solenoid up to remove and reinstall it. Lastly, the EVAP canister, situated atop the fuel tank, requires raising the vehicle, disconnecting electrical connectors and labeled hoses, then detaching it from its mounting bracket for removal and installation. The fuel tank pressure sensor, located on top of the fuel pump/fuel level sensor module mounting flange, involves raising the vehicle, removing the fuel tank, disconnecting the electrical connector, and then removing and reinstalling the sensor.