Originally Posted by Black_Box
It captures fuel vapors and prevents them from escaping to the atmosphere and then stores the fumes and recycles them to the fuel tank or engine intake for combustion as needed.
What he said LOL!
The Evaporative Control (EVAP) System captures any raw fuel evaporating from the fuel storage system (e.g. the fuel tank, the filler neck, and fuel cap). Under precise operating conditions dictated by engine temperature, speed, and load, the EVAP system stores and purges these captured fuel vapors back into the combustion process.
How Part Functions in The System
The Evaporative Control System is designed to not only capture, store and purge any raw fuel vapors that leak from any areas of the Fuel Storage System but also to run a series of self-tests that confirm or deny the Operational and Vapor Holding ability of the System.
The Charcoal Canister is the vapor holding device for the Evaporative System. It is usually a plastic enclosure that contains a large block of Activated Charcoal. Activated Charcoal is Charcoal that has been treated with Oxygen to greatly increase its ability to absorb and hold Fuel Vapors by opening up tiny pores between the Carbon atoms that make up ordinary Charcoal. The containment of Fuel Vapor is an important task because at least 20% of the Vehicle produced Air Pollution originates from malfunctioning Vehicle Fuel Storage Systems. If it weren't for the presence and vapor holding ability of the Charcoal Canister, the Fuel Vapors would leak into the atmosphere. The Charcoal Canister can be located by the Fuel Tank, in the Engine Compartment or inside a front or rear Fender. Since the Charcoal Canister is subjected to moisture and temperature changes, its vapor holding ability must be leak tested on a daily basis
There are many ways for vehicles to 'leak test' the components in the Evaporative System, but most perform the leak test either when the vehicle is sitting, say over night, or shortly after initial start up after the vehicle has been sitting over night. The Evaporative Systems operational performance is also tracked by the Power Train Computer by reading the change in the Oxygen Sensor voltages and Short Term Fuel Trim when ever the stored Vapors are released or 'purged' back into the combustion process. These values should indicate that fuel is being added to the system and that the over all mixture is getting richer. The purging process occurs when the vehicle is under acceleration, which is when most vehicles require additional fuel.
Originally Posted by PCH
I wonder if there is a warranty coverage for something like this in Ohio. This is what i found for a different vehicle (that should't be different for xB though): 2005 model year Highlander charcoal canister is covered under the California
Emission Warranty. This warranty is in effect for 84 months or 70,000 miles,
whichever occurs first, from the vehicle’s in-service date.
From TSB: http://www.toyotapart.com/M.I.L._ON_...T-EG043-06.pdf
Unfortunately, this doesn't look like it would be covered by the Federal Emissions Warranty (8 yrs / 70K miles) since it's not listed as a major component of the emissions system.
There are three specified major emission control components,
covered for the first 8 years or 80,000 miles of vehicle use on 1995
and newer vehicles:
* Catalytic converters.
* The electronic emissions control unit or computer (ECU).
* The onboard emissions diagnostic device or computer (OBD).