Question about 2007 Chevrolet Uplander
I have alot of hoses can i put it far away from the evap canister thank you have a good day.denis email email@example.com
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Posted on Jan 02, 2017
DTC P0446 Evaporative Emission (EVAP) Vent System Performance
The vehicle control module (VCM) monitors the performance of the evaporative emission (EVAP) system by applying a predetermined level of vacuum to the EVAP system and monitors the vacuum decay rate. The VCM sets this diagnostic trouble code (DTC) if the vacuum decay rate is more than a predetermined value. The VCM monitors the amount of vacuum and the amount of pressure in the EVAP system by monitoring the fuel tank pressure sensor. For this DTC, the VCM turns ON both the EVAP purge valve and the EVAP vent valve when the Conditions for Running the DTC are met. This applies an engine vacuum to a closed EVAP system. The VCM turns OFF both the EVAP purge valve and the EVAP vent valve when the system reaches a correct amount of vacuum. The EVAP system should quickly RELEASE the vacuum in the EVAP system with the EVAP purge valve OFF and the EVAP vent valve OFF (open). This test indicates a blocked or restricted EVAP vent path if the EVAP system fails to release the vacuum quickly enough.
Posted on Dec 06, 2008
if you look underneath the vehicle on drivers side in the area beneath drivers you with see a plastic rectangular sort of shaped box this is evap canister and vent valve is there in this area.
Posted on Jun 20, 2009
I would bring it back to the shop that did the work. If the code is coming out as a problem with the evap system it is not abnormal for the system to take 2 or 3 days for it to read again.
Posted on Mar 30, 2010
in my experience the usual culprit is the evap cannister. the problem is it gets moisture in it and freezes during winter thus cracking the plastic. if you lay under the car and look at the evap box it black plastic and if you see a loose or cracked hose or the box itself is cracked that is most likely it. as a side note you can check the gas cap and buy a new one to see if that rectifies the situation. lastly i don't think the gas tank should be suspect as you would probably notice if gas was leaking out of the tank. if you take the car to a dealer or shop they can do a smoke test and determine where the leak is.
Posted on Oct 19, 2010
A leak in the EVAP system can be a pain to resolve so be methodical. Start with the junction of the tube from the purge valve to the inlet manifold plenum. Disconnect this tube and block off the exposed port on the manifold. A great way for blocking off tubes and ports is to cut off the fingers of a rubber washing up glove and elastic bands to secure them over the exposed ends.
First let us recap on the system. The
EVAP system passively stores fuel vapour from the fuel tank in a charcoal filled
canister. The canister can be located on the fender or bulkhead. When the engine is running
above idle speed the ECU opens a purge valve connecting a pipe to the
throttle body. A corresponding vent valve allows the
ingress of air into the canister and this encourages fuel vapour to be drawn
out of the canister through the purge valve to the throttle air intake
mixture and thereafter to be burnt. The opening of the
purge valve cycles with engine speed.
The purge valve should be closed during idle. A faulty EVAP system manifest itself as erratic idling as it allows un-metered air into the system and compromises the inlet manifold vacuum. The blocking of the ports as initially suggested above should at least cause any erratic idling to be resolved.
The EVAP system is not critical to engine performance, it is an emission control device, so the car may be run without issue until the fault is found. Look at the fuel cap, ensure that the rubber seal is intact. To make doubly sure give it a smear of grease. Next look at the disconnected 'purge valve to throttle' tube. Inspect it thoroughly for cracks, be quite rough and twist it around to get a good look. Now locate the purge valve. If it is electrically operated simply check for voltage continuity across its connector pins. An open circuit indicates a burnt out solenoid winding. Check the connection to the canister. Check the vent valve connections, and again check its electrical continuity. Check the tank to canister tubing and any connections.
If you find no leaks you may need to take it to a garage that can do a smoke test on the system - this highlights the leaks as wisps of smoke appear where the leaks occur.
Posted on Dec 01, 2010
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