DTC P0446 Evaporative Emission Control System Vent Control Circuit

DTC P0446 EVAPORATIVE EMISSION CONTROL SYSTEM VENT CONTROL CIRCUIT

CIRCUIT DESCRIPTION

DTC Detection Condition:

P0446
The VSV for CCV is open under normal conditions. When the VSV for EVAP is used to purge the evaporative emissions from the fuel tank into the intake manifold, air is drawn from the charcoal canister into the fuel tank. Also, the VSV for CCV has a function that relieves the pressure in the case that the pressure inside the fuel tank has rapidly increased. Also, it creates a vacuum inside the fuel tank in unison with the operation of the VSV for EVAP and leak tests are performed using this vacuum.

When the VSV for CCV remains closed (closed malfunction), the vacuum created inside the fuel tank cannot be relieved. When the VSV for CCV remains open (opened malfunction), it cannot create a large vacuum.

EVAP LEAK TEST
a. Connect the hand-held tester to the DLC3.
b. Select the item "ENHANCED OBD II/SYSTEM CHECK/EVAP SYS CHECK (or EVAP LEAK TEST)" mode on the hand-held tester.

c. If any changes do not occur within 1 minute after pressing "EVAP LEAK TEST", remove the fuel tank cap, then set the fuel tank cap again. Perform "EVAP SYS CHECK (or EVAP LEAK TEST)".

HINT: If a leak is detected during this leak test, or if DTCs P0441, P0442 and P0446 were output simultaneously, conduct a leak test again after repair. If no leak is found at this time, the EVAP system is recovered to normal.

Wiring Diagram:

CONFIRMATION READINESS TEST

First Trip Procedure

a. The vehicle must be cold, and the ambient temperature must be approximately between 50 to 95°F.
b. The Intake Air Temp. (IAT) and the Engine Coolant Temp. (ECT) sensors have almost the same value.

c. Clear the DTCs.
- Disconnect the battery terminal or remove the EFI and ETCS fuses more than 60 sec.
- Readiness tests will show INCMPL (incomplete).

d. Drive the vehicle according to the LA#4 driving cycle. Note 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 min. 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 Tests show Pass7 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 50 to 95°F.
f. Go to Readiness Tests screen.
g. Drive the vehicle according to LA#4 drive cycle. Note 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 (Purge Flow), P0446 (VSV for CCV), P0451, P0452 or P0453 (Evaporative Pressure Sensor) 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.

- Ask the customer whether, after the MIL came on, the customer found the fuel tank cap loose and tightened it. Also ask the customer whether the fuel tank cap was loose when refuelling. If the fuel tank cap was loose, it was the cause of the DTC. If the fuel tank cap was not loose or if the customer was not sure if it was loose, troubleshoot according to the following procedure.

- Read freeze frame data using the hand-held tester or the OBD II scan tool, as 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.