P0446

DTC P0446 Evaporative Emission Control System Vent Control Malfunction

CIRCUIT DESCRIPTION

DTC Detecting Condition:

The vapor pressure sensor, VSV for canister closed valve (CCV), VSV for pressure switching valve are used to detect abnormalities in the evaporative emission control system.

The ECM decides whether there is an abnormality in the evaporative emission control system based on the vapor pressure sensor signal.

DTCs P0441 and P0446 are recorded by the ECM when evaporative emissions leak from the components within the dotted line in Fig. 1, or when there is a malfunction in either the VSV for EVAP, the VSV for pressure switching valve, or in the vapor pressure sensor itself.

P0446
When the vapor pressure rises to a specified point, the ECM opens the VSV for CCV Pressure will increase rapidly because of the air allowed into the system. No increase or an increase below specified rate of pressure increase indicates a restriction on the air inlet side.

The ECM closes the VSV for pressure switching valve. This action blocks air entering the fuel tank side of system. The pressure rise on the fuel tank side is no longer as great.

If there is no change in pressure, the ECM will conclude the VSV for pressure switching valve did not close.






HINT: Typical DTC output of each trouble part

Wiring Diagram:

INSPECTION PROCEDURE

HINT:
- If DTC P0441, P0446, P0450 or P0451 is output after DTC P0440,first troubleshoot DTC P0441, P0446, P0450 or P0451. If no malfunction is detected, troubleshoot DTC P0440 next.
- Read freeze frame data using hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.
- When the ENGINE RUN TIME in the freeze frame data is less than 200 seconds, carefully check the VSV for EVAP charcoal canister and vapor pressure sensor.

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Hand-held tester:

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OBD II scan tool (excluding hand-held tester):