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) 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 or in the vapor pressure sensor itself.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Monitor Result (MODE 06 DATA):

The ECM tests the evaporative emissions (EVAP) system using the fuel tank pressure sensor, the canister close valve (CCV), and the VSV for EVAP. The ECM closes the EVAP system and introduces a negative pressure (vacuum) into it. The ECM then monitors the internal pressure using the fuel tank pressure sensor.

P0446
The VSV for CCV is open under normal operating conditions. When the VSV for EVAP is used to purge the evaporative emissions from the fuel tank into the intake manifold, fumes are drawn from the fuel tank into the charcoal canister. The VSV for CCV has an additional function that relieves the pressure when the pressure inside the fuel tank has rapidly increased. Finally, the VSV for CCV is used in unison with the VSV for EVAP to create a vacuum inside the fuel tank and leak tests are performed using this vacuum.

If the VSV for EVAP is stuck closed, or the negative pressure inside the fuel tank increased despite the CCV opening, the ECM illuminates the MIL and sets the DTC.

Wiring Diagram:

CONFIRMATION READINESS TEST

First Trip Procedure
a. The vehicle must be cold, and the ambient temperature must be approximately between 10 and 35°C (50 and 95°F).
b. The Intake Air Temperature (IAT) and the Engine Coolant Temperature (ECT) sensors have almost the same value.

c. Clear the DTCs.
- Disconnect the battery terminal or remove the EFI fuse for more than 60 seconds.
- Readiness tests will show "INCMPL" (incomplete).

d. Drive the vehicle on a freeway. Write down the state of the Readiness Tests. They will change to COMPL as the EVAP evaluation monitors operate and if the system passes. This procedure may take approximately 20 minutes or more.

NOTE: Do not shut off the engine - the results will be invalid.

Pass Condition - No Problem Found by the ECM

If the EVAP evaluation monitor shows "COMPL", go to the Non- Continuous Test screen.

NOTE: Do not shut off the engine - the results will be invalid.

- To get there, go to Advanced OBD II, Onboard Tests, Non-continuous Tests.
- If all of the tests in the time $02 category show "Pass", the EVAP evaluation monitor has operated and no problem was detected.

Fail Condition - Problem Detected by the ECM

If the EVAP evaluation monitor shows INCMPL, go to the Non-Continuous Test screen.

1. If all Tests show "Pass", the following may have occurred.
- The EVAP evaluation monitor did not operate.
- The EVAP evaluation monitor did not finish.
- The ECM withheld judgement.

2. If one or more of the tests in the time $02 category show "Fail", the EVAP evaluation monitor did operate and the ECM detected a problem.

3. Go to Continuous Tests screen. This is the only place DTC's are listed for the first trip.

NOTE: The DTC listed may not be valid. A second trip is needed to confirm the DTC.

Second Trip Procedure

e. The vehicle must be cold, and the ambient temperature must be approximately between 10 and 35°C (50 and 95°F).
f. Go to Readiness Tests screen.
g. Drive the vehicle on a freeway. Write down the state of EVAP evaluation monitor. This procedure may take approximately 20 minutes or more.

NOTE: Do not shut off the engine - the results will be invalid.

h. If Readiness Tests changes to "COMPL", the EVAP evaluation monitor has operated. Check for any stored DTC's.
- If a DTC has stored, the problem has been detected and confirmed by the ECM.
- If no DTC was found, the EVAP monitor operated but no problem was detected.

INSPECTION PROCEDURE

HINT:
- If DTC P0441, P0446 or P0451 is output with DTC P0442 or P0456, first troubleshoot DTC P0441, P0446 or P0451. If no malfunction is detected, troubleshoot DTC P0442 or P0456 next.
- Read freeze frame data using hand-held tester or the OBD II scan tool. 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 vapor pressure sensor.