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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1387 (Engine Control System Diagnosis (DTC P0130 To DTC P0456) -- 1.8L (LV6)) >> Diagnosis >> DTC P0446 >> System Description

System Description

WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

When running the DTC P0446 Evaporative Emission (EVAP) Vent System Performance diagnostic the powertrain control module (PCM ) monitors the fuel tank pressure (FTP) sensor. When vapor pressure rises to a specified value, the PCM commands the vent valve open, and monitors the FTP sensor signal. Pressure will increase rapidly because of the air allowed into the system. No increase or an increase below a specified rate indicates a restriction on the air inlet side. The PCM then commands the pressure switching solenoid closed. This blocks air from entering the tank side of the system. The PCM monitors the FTP sensor and looks for a decrease in the pressure rise. If there is no change in pressure the PCM concludes the pressure switching solenoid did not close. If the PCM does not detect an increase in pressure, or the rise in pressure does not change, a DTC P0446 will set.

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