P0446

DTC P0446 EVAPORATIVE EMISSION CONTROL SYSTEM VENT CONTROL CIRCUIT

CIRCUIT DESCRIPTION

DTC Detection Condition:

The vapor pressure sensor, Canister Closed Valve (CCV), pressure switching VSV are used to detect abnormalities in the Evaporative Emissions (EVAP) control system.

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

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

HINT: Typical DTC output of each trouble part.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Monitor Result (Mode 06 Data):

P0446
If there is a malfunction detected in the EVAP VSV, the CCV and the pressure switching VSV, the ECM will illuminate the MIL and set a DTC.

This portion of the EVAP diagnosis checks the following EVAP system functions:
a. CCV stuck closed.
The ECM checks for a CCV stuck closed malfunction by commanding the CCV to open after an EVAP leak test. If the fuel tank pressure does not rise (loss of vacuum), the ECM determines that the CCV is stuck closed. The ECM will turn on the MIL and a DTC is set.

b. Pressure switching VSV stuck closed.
The ECM checks for a pressure switching VSV stuck closed malfunction by commanding the pressure switching VSV to close after an EVAP leak test. If the fuel tank pressure does not change, the ECM determines that the pressure switching VSV is malfunctioning. The ECM will turn on the MIL and a DTC is set.

c. EVAP VSV (purge line to intake manifold) stuck closed.
The ECM checks for a stuck closed malfunction in the EVAP VSV by commanding it to open with the CCV closed. If a high negative pressure does not develop in the fuel tank, the ECM determines that the EVAP VSV remains closed. The ECM turns on the MIL and a DTC is set.

Wiring Diagram:

INSPECTION PROCEDURE

HINT:
- Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, as well as other data from the time when a malfunction occurred.
- When the ENGINE RUN TIME in the freeze frame data is less than 200 seconds, carefully check the vapor pressure sensor.