P0446

1NZ-FXE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0446: Evaporative Emission Control System Vent Control Circuit

DTC P0446 - Evaporative Emission Control System Vent Control Circuit

DESCRIPTION





This DTC is designed to detect the purge flow switching valve (3-way VSV) malfunction. If the malfunction is detected while the vehicle is running, the ECM illuminates the MIL and sets a DTC (2 detection logic).
The purge flow switching valve located on the canister is used to detect leakage from the bladder tank into the fuel tank. The valve opens during the bladder tank leak check. Then, the fuel tank's fuel vapor flows to the intake manifold without passing the canister.

MONITOR DESCRIPTION

Purge flow switching valve is stuck OFF (Closed)

The purge flow switching valve opens when the purge VSV opens while the vehicle is running. Then, the fuel tank pressure drops 2 mmHg or more when the purge flow switching valve is normal. If the pressure does not change, the ECM interprets this as a malfunction. The ECM illuminates the MIL and sets a DTC (2 trip detection logic).

Purge flow switching valve is stuck ON (Open)

In order to depressurize the fuel tank, the pump module's vent valve is turned ON (close) when the purge VSV opens while the vehicle is running. After the fuel tank pressure drops 20 mmHg, the purge VSV closes. Then, the fuel tank pressure rises slightly when the purge flow switching valve is normal. If the pressure rises quickly, the ECM interprets this as a malfunction. The ECM illuminates the MIL and sets a DTC (2 trip detection logic).

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





WIRING DIAGRAM









INSPECTION PROCEDURE

PROCEDURE

1. CONFIRM DTC
(a) Turn the power switch OFF and wait for 10 seconds.
(b) Turn the power switch ON (IG).
(c) Turn the power switch OFF and wait for 10 seconds.
(d) Connect Techstream to the DLC3.
(e) Turn the power switch ON (IG).
(f) Enter the following menus: Powertrain / Engine and ECT / Trouble Code.
(g) Check if DTC P0446 is output.
NO -- PERFORM EVAPORATIVE SYSTEM CHECK
YES -- Continue to next step.

2. PERFORM EVAPORATIVE SYSTEM CHECK
(a) Note the freeze frame data and DTCs.
(b) Clear the DTCs DTC Check / Clear.
(c) Enter the following menus: Powertrain / Engine and ECT / Utility / Evaporative System Check / Automatic Mode.
(d) After the system check is finished, check for pending DTCs.
OK:
No DTC is present.
NG -- CHECK DTC
OK -- Continue to next step.

3. CHECK OPERATION OF PURGE FLOW SWITCHING VALVE
(a) Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VSV for Tank Bypass.
(b) Touch the purge flow switching valve (TANK BYPASS VSV) to feel the operating vibration.
OK:
The purge flow switching valve is operated by the Active Test.
NG -- CHECK HARNESS AND CONNECTOR (PURGE FLOW SWITCHING VALVE - ECM AND EFI M RELAY)
OK -- Continue to next step.

4. CHECK PURGE FLOW SWITCHING VALVE




(a) Turn the power switch OFF.
(b) Remove the purge flow switching valve.
(c) Reconnect the purge flow switching valve connector.
(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VSV for Tank Bypass.
(e) Check the airflow for the purge flow switching valve.
OK:
The purge flow switching valve operates normally.
OK -- REPLACE HOSE (PURGE FLOW SWITCHING VALVE AND FUEL TANK)
NG -- REPLACE PURGE FLOW SWITCHING VALVE
5. PERFORM EVAPORATIVE SYSTEM CHECK
(a) Enter the following menus: Powertrain / Engine and ECT / Utility / Evaporative System Check / Automatic Mode.
(b) After the system check is finished, check for pending DTCs.
OK:
DTCs are present.
NG -- CHECK FOR INTERMITTENT PROBLEMS
OK -- Continue to next step.

6. CHECK DTC
(a) Check the DTCs that were present in the EVAP system check.
OK:
P043E, P043F, P2401, P2402 and P2419 are present.
NG -- CHECK DTC
OK -- Continue to next step.

7. CHECK VENT VALVE CLOSE STUCK
(a) Allow the engine to idle.
(b) Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VSV for EVAP Control.
(c) Turn the EVAP VSV ON (purge VSV open) and check the VAPOR PRESS (EVAP pressure) for 10 seconds.
OK:
EVAP pressure is higher than 755 mmHg.
NG -- CHECK FOR VENT HOSE CLOG
OK -- Continue to next step.

8. CHECK LEAK DETECTION PUMP OPERATION
(a) Turn the power switch OFF.
(b) Turn the power switch ON (IG).
(c) Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the Vacuum Pump.
(d) Touch the pump module to feel the operating vibration.
OK:
The leak detection pump is operated by the Active Test.
NG -- CHECK HARNESS AND CONNECTOR (CANISTER PUMP MODULE - ECM)
OK -- Continue to next step.

9. CHECK TRAP CANISTER




(a) Disconnect the vent hose from the pump module.
(b) Check that no moisture is in the pump module or the vent hose.
OK:
No moisture.
NG -- CHECK FOR VENT HOSE DAMAGE
OK -- REPLACE TRAP CANISTER WITH PUMP MODULE
10. CHECK DTC
(a) Check the DTCs that were present in the EVAP system check.
OK:
P0441, P0455 and/or P0456 are present.
NG -- CHECK DTC
NG -- Continue to next step.

11. CHECK INSTALLATION CONDITIONS OF FUEL CAP
(a) Remove the fuel cap.
(b) Reinstall the fuel cap.
(c) Clear the DTCs DTC Check / Clear.
(d) Enter the following menus: Powertrain / Engine and ECT / Utility / Evaporative System Check / Automatic Mode.
(e) After the system check is finished, check for pending DTCs.
HINT: If no DTC is present, this indicates that the fuel cap is loosened.

OK:
No DTC is present.
OK -- REPAIR COMPLETED
NG -- Continue to next step.

12. LOCATE LEAK POINT
(a) Disconnect the vent hose (fresh air line) as shown in the illustration.




(b) Connect the pressure gauge and air pump as shown in the illustration.
(c) Pressurize the EVAP system until the pressure reaches 24 to 28 mmHg.
(d) Locate the leak point.
HINT: If the EVAP system has leakage, a whistling sound may be heard.

OK:
The leak point is found.
OK -- REPAIR OR REPLACE LEAK POINT
NG -- Continue to next step.

13. CHECK FUEL CAP
(a) Check that the fuel cap meets OEM specifications.
HINT: If an EVAP tester is available, perform the fuel cap test according to the tester's instructions.

OK:
Fuel cap meets OEM specifications.
NG -- REPLACE FUEL CAP
OK -- Continue to next step.

14. CHECK OPERATION FOR PURGE VSV
(a) Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VSV for EVAP Control.
(b) Touch the purge VSV to feel the operating vibration.
OK:
The purge VSV (EVAP VSV) is operated by the Active Test.
NG -- CHECK HARNESS AND CONNECTOR (PURGE VSV - ECM)
OK -- Continue to next step.

15. CHECK INTAKE MANIFOLD PRESSURE




(a) Disconnect the purge VSV hose that is connected to the throttle body.
(b) Allow the engine to idle.
(c) Check that the hose has suction using your finger.
OK:
The hose has suction.
OK -- REPLACE PURGE VSV
NG -- REPLACE HOSE (PURGE VSV - THROTTLE BODY)
16. CHECK DTC
(a) Check the DTCs that were present in the EVAP system check.
OK:
P0451 is not present.
NG -- CHECK TRAP CANISTER
OK -- Continue to next step.

17. CHECK OPERATION FOR VENT VALVE
(a) Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VSV for Vent Valve.
(b) Touch the pump module to feel the operating vibration.
OK:
The vent valve is operated by the Active Test.
NG -- CHECK HARNESS AND CONNECTOR (CANISTER PUMP MODULE - ECM)
OK -- CHECK TRAP CANISTER
18. CHECK HARNESS AND CONNECTOR (PURGE FLOW SWITCHING VALVE - ECM AND EFI M RELAY)
(a) Check the harness and the connectors between the purge flow switching valve and the ECM.





(1) Disconnect the V8 purge flow switching valve connector.





(2) Disconnect the E7 ECM connector.
(3) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):






Standard resistance (Check for short):






(4) Reconnect the purge flow switching valve connector.
(5) Reconnect the ECM connector.
(b) Check the harness and the connectors between the purge flow switching valve and the EFI M relay.
(1) Disconnect the V8 purge flow switching valve connector.





(2) Remove the integration relay from the engine room relay block.
(3) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):






Standard resistance (Check for short):






(4) Reconnect the purge flow switching valve connector.
(5) Reinstall the integration relay.
OK -- REPLACE ECM
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
19. REPLACE PURGE FLOW SWITCHING VALVE
(a) Replace the purge flow switching valve Locations.
NEXT -- PERFORM EVAPORATIVE SYSTEM CHECK
20. CHECK FOR VENT HOSE CLOG
(a) Turn the power switch OFF.




(b) Disconnect the vent hose (fresh air line) as shown in the illustration.
(c) Allow the engine to idle.
(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VSV for EVAP Control.
(e) Turn the purge VSV (EVAP VSV) ON and check the EVAP pressure (VAPOR PRESS) for 10 seconds.
OK:
EVAP pressure is higher than 755 mmHg.
OK -- CHECK AND REPLACE VENT HOSE OR CANISTER FILTER
NG -- REPLACE TRAP CANISTER WITH PUMP MODULE
21. CHECK HARNESS AND CONNECTOR (CANISTER PUMP MODULE - ECM)




(a) Disconnect the V7 canister pump module connector.




(b) Disconnect the E7 ECM connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):






Standard resistance (Check for short):





(d) Reconnect the canister pump module connector.
(e) Reconnect the ECM connector.
OK -- REPLACE ECM
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
22. REPLACE TRAP CANISTER WITH PUMP MODULE
(a) Replace the trap canister with pump module Removal.
NEXT -- PERFORM EVAPORATIVE SYSTEM CHECK
23. CHECK FOR VENT HOSE DAMAGE
Check for hose damage as shown in the illustration. If necessary, replace the vent hose.





NEXT -- REPLACE TRAP CANISTER WITH PUMP MODULE
24. REPAIR OR REPLACE LEAK POINT
NEXT -- PERFORM EVAPORATIVE SYSTEM CHECK
25. REPLACE FUEL CAP
NEXT -- PERFORM EVAPORATIVE SYSTEM CHECK
26. CHECK HARNESS AND CONNECTOR (PURGE VSV - ECM)




(a) Disconnect the V1 purge VSV connector.




(b) Disconnect the E5 ECM connector.
(c) Check the harness and the connectors between the ECM and the purge VSV connectors.
(1) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):






Standard resistance (Check for short):









(d) Remove the integration relay from the engine room relay block.
(e) Check the harness and connectors between the purge VSV connector and the EFI M relay.
(1) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):






Standard resistance (Check for short):





(f) Reconnect the purge VSV connector.
(g) Reconnect the ECM connector.
(h) Reinstall the integration relay.
OK -- REPLACE ECM
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
27. REPLACE HOSE (PURGE VSV - THROTTLE BODY)
NEXT -- PERFORM EVAPORATIVE SYSTEM CHECK
28. REPLACE PURGE VSV
(a) Replace the purge VSV Locations.
NEXT -- PERFORM EVAPORATIVE SYSTEM CHECK
29. CHECK HARNESS AND CONNECTOR (CANISTER PUMP MODULE - ECM)




(a) Disconnect the V7 canister pump module connector.




(b) Disconnect the E7 ECM connector.
(c) Check the harness and the connectors between the ECM and the canister connectors.
(1) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):






Standard resistance (Check for short):









(d) Remove the integration relay from the engine room relay block.
(e) Check the harness and connectors between the canister connector and the EFI M relay.
(1) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):






Standard resistance (Check for short):





(f) Reconnect the canister pump module connector.
(g) Reconnect the ECM connector.
(h) Reinstall the integration relay.
OK -- REPLACE ECM
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
30. REPAIR OR REPLACE HARNESS OR CONNECTOR
NEXT -- PERFORM EVAPORATIVE SYSTEM CHECK
31. REPLACE ECM
(a) Replace the ECM Removal.
NEXT -- PERFORM EVAPORATIVE SYSTEM CHECK
32. CHECK AND REPLACE VENT HOSE OR CANISTER FILTER
NEXT -- PERFORM EVAPORATIVE SYSTEM CHECK
33. REPLACE HOSE (PURGE FLOW SWITCHING VALVE AND FUEL TANK)
NEXT -- Continue to next step.

34. PERFORM EVAPORATIVE SYSTEM CHECK
(a) Turn the power switch ON (IG).
(b) Enter the following menus: Powertrain / Engine and ECT / Utility / Evaporative System Check / Automatic Mode.
(c) After the system check is finished, check for pending DTCs.
OK:
No DTC is present.
NG -- CHECK DTC
OK -- Continue to next step.

35. PERFORM EVAP MONITOR DRIVE PATTERN
(a) Check that the following conditions are met:

- Fuel level is 1/8 to 7/8.
- Engine coolant temperature (ECT) is 4.4 to 35°C (40 to 95°F).
- Intake air temperature (IAT) is 4.4 to 35°C (40 to 95°F).
- Difference between ECT and IAT is less than 7°C (44°F).
(b) Enter the check mode. Enter the following menus: Powertrain / Engine and ECT / Utility / Check Mode.
(c) Allow the engine to idle until the ECT is 75°C (167°F).
(d) Drive the vehicle at 30 mph (48 km/h) or faster and maintain that speed for 60 seconds or more.
(e) Stop the vehicle. Do not turn the power switch OFF.
(f) Check that the EVAP monitor status is complete. Enter the following menus: Powertrain / Engine and ECT / Monitor / Evaporative System.
(g) If the EVAP monitor is incomplete, drive the vehicle at 30 mph (48 km/h) or faster and maintain that speed for 120 seconds or more. After that, recheck the EVAP monitor status.
(h) Check for pending DTCs.
OK:
No DTC is present.
NG -- PERFORM EVAPORATIVE SYSTEM CHECK
OK -- REPAIR COMPLETED