P0446

DTC P0446 EVAPORATIVE EMISSION CONTROL SYSTEM VENT CONTROL CIRCUIT

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 malfunction in either VSV for EVAP and VSV for pressure switching valve, 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 VSV for evaporative emission (EVAP), the canister closed valve (CCV) and the VSV for bypass valve; 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 (lose vacuum), the ECM determines that the CCV is stuck closed. The ECM will turn on the MIL and a DTC is set.

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

c. VSV for EVAP (Purge line to intake manifold) stuck closed.
The ECM checks for a stuck closed malfunction in the VSV for EVAP 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 VSV for EVAP remains closed. The ECM turns on the MIL and a DTC is set.

Wiring Diagram:

INSPECTION PROCEDURE

HINT:
- If DTC P0441 (Purge Flow), P0446 (VSV for CCV or VSV for Pressure switching valve), P0451, P0452 or P0453 is output with DTC P0442 or P0456, first troubleshoot DTC P0441, P0446, P0451, P0452 or P0453. If no malfunction is detected, troubleshoot DTC P0442 or P0456 next.
- 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, 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 vapor pressure sensor.