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Old 07-18-2008, 12:39 PM
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P0440 EVAP System No Flow During Purge

Does the MIL go off after you fill the tank, and then come back on after you drop below 1/2 a tank? If so, your code is caused by a filter on the evap purge pump. In '99 up to '03-4 trucks, they put these on the frame right where they could collect mud and road grime, ect. When they plug, the evap pump cannot draw in fresh air, upsetting the pressure in the system, and sets P0440. The pump kicks on after the fuel level drops below 1/2 a tank. Unfortunatley, in '99 you cant remove the darn thing to clean it, and it used to cost around $300 for the filter relocation kit.

Last edited by sbchevfreak; 07-18-2008 at 12:42 PM. Reason: Add information
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