I have a 2000 Toyota Echo with a P0440 code on the check engine light. The Vapor Cannister (and all the valves attached to it) have been replaced. The Gas Cap has been replaced. The VSV has been taken out, tested, cleaned, and replaced. It has been smoke tested and no leaks were found. The new gas cap has been turned until it clicks and is as tight as I can make it. Any Suggestions?

code p0440 refers to evaporative emission (EVAP) system--malfunction=== causes --hose connections --intake leak--EVAP canister purge valve
code po441 refers to EVAP --incorrect flow detected==causes the same as for po440
code po446 refers to EVAP system vent control --circuit malfunction===causes --wiring---EVAP can purge valve--ECM
generally I would replace the purge valve as it is common to all codes

under the rear of the vehicle under the trunk

P0440 EVAP mulfunction , EVAP valve or hoses leak

take it to autozone and have the fault codes read for free
the charcoal cannister that they speak of is the EVAP cannister and if there is a problem with it it will show as a fault code
it has a purge valve and a purge valve solenoid for operation , both of which can be replaced separately
when you hear" I think " , time to find an accredited service center that has experience on your make pf vehicle and get a second opinion
the gas tank neck is a rubber section and comes up in the code as a small leak
a simple loose gas cap will put the light on

P0440 Evaporative Emission Control System Malfunction P0441 Evaporative Emission Control System Incorrect Purge Flow P0446 Evaporative Emission Control System Vent Control Circuit Malfunction

• Remove and reinstall the gas cap, clear the code, and drive for a day and see if the codes come back.
• Inspect the EVAP system for cuts/holes in tubes/hoses
• Inspect for damaged or disconnected hoses around the Evap purge solenoid
• Check and/or replace the sensor
• Check and/or replace the purge valve
• Have a professional use a smoke machine to detect leaks

Start with the simple and replace the gas cap, and see if the check engine light goes out after a day or so. Post me back the DTC codes just to make sure it's not the EVAP purge valve on the intake manifold by the ignition coil.
Thank you for using fixya and good luck

the most common cause of this in Nissan is a defective carbon cannister vapor purge valve in the evaporative emission control system.

P0441 - Evaporative Emission Control System Incorrect Purge Flow The "EVAP purge flow" faults are issues between the carbon cannister and the intake. The EVAP leak detection generally concerns the fuel tank to carbon cannister plumbing. A little background. The EVAP or evaporative emission system is a control system to keep vapors from evaporation in the fuel tank from getting into the atmosphere. The fuel tank is not vented, but rather the vapors are piped to the carbon cannister (usually located behind the pass. side front wheel) where the charcoal element absorbs the vapor. This is actually a vapor "storage" device. Under certain engine operating conditions, the ECU activates the Cannister Purge Valve (N80) which opens and allows the engine vacuum to **** the fuel vapors back out of the carbon cannister. This purges the vapor, allowing the cannister to absorb more vapor. This evap system has been on vehicles since the '70s. As part of the OBDII standard effective for 1996 cars and newer, it was mandated that leaks in the systems must be detected and reported as a fault which will set the Check Engine Light (CEL). To detect leaks, the system is pressurized by a pump so that leaks can be detected by a lack of appropriate pressure in the system. If there is a leak, such as a cracked vent hose, loose (or leaky) gas cap, poorly installed or defective O-rings on the fuel level senders on the fuel tank, etc. a code will be set. On the cannister to intake side, leaks are detected by deviations in the idle control system. If you have leaks in the lines from the carbon cannister to the intake, intake leaks, a defective purge valve, etc you will often get purge flow faults. My first recommendation is to closely inspect all the small vacuum lines connected to the intake manifold. The corrugated plastic lines are often the culprits, as well as the fabricate covered vacuum lines. Also consider replacing the gas cap.

where is Evap Emission Control System Purge Flow fault

p0440 code means that the evap system has a leak. This could be caused by a bad or improperly installed gas cap. Either that or the purge solenoid has failed or the canister is plugged and not working properly.