DTC P0446 Evaporative Emission (EVAP) Vent System Performance
Refer to EVAP Control System Overview .
System Description
This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge valve ON and the EVAPcanister vent valve ON. This allows a vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canisterpurge valve OFF and the EVAP canister vent valve OFF. The control module monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, this DTC sets.
P0446 Evaporative Emission Control System Vent Control Circuit Malfunction The code P0446 is set when the engine computer recognizes a fault or restriction at the vent control part of the Evaporative emission control system (EVAP). The description of the fault varies between different car manufacturers, but one thing is common, the code P0446 doesn't directly point to a defective part; some testing might be required to pinpoint the faulty component. What can cause the code P0446: - faulty vent control valve - blockage at the vent hose, vent filter or vent control valve - open or short in the vent control valve circuit - bad charcoal canister - EVAP system leak - faulty EVAP system pressure sensor - bad vacuum switching valve (VSV) - stuck open purge valve (solenoid)
Evaporative Emission Control System Vent Control Circuit Malfunction
What does that mean?
Evap vent valve has only one purpose. It closes in order to seal the vent so
the EVAP system can pressurize and ensure there are no leaks. Evap vent valve
is usually supplied Batt. voltage with key on. The ECM's driver controls the
ground, and when grounded, activates the valve (closing it). If the ECM detects
a short to ground, and open,or a short to battery voltage on the control circuit,
P0446 will set. Code also may refer to ECM detecting that EVAP system is unable
to achieve or maintain vacuum during test.
Symptoms
There will be no obvious symptoms to driver, other than MIL illumination.
Causes
A code P0446 could mean one or more of the following has happened:
P0446....Evaporative Emission Control System Vent Control Circuit
something is wrong with vapour control system ,could just be a `perished rubber pipe along the line somewhere and you will have to look and check it all ,and renew the pipe as necessary
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