P1491

Component Description
The vacuum cut valve and vacuum cut valve bypass valve are installed in parallel on the EVAP purge line between the fuel tank and the EVAP canister.
The vacuum cut valve prevents the intake manifold vacuum from being applied to the fuel tank.
The vacuum cut valve bypass valve is a solenoid type valve and generally remains closed. It opens only for on board diagnosis. The vacuum cut valve bypass valve responds to signals from the ECM. When the ECM sends an ON (ground) signal, the valve is opened. The vacuum cut valve is then bypassed to apply intake manifold vacuum to the fuel tank.

EVAPORATIVE EMISSION SYSTEM DIAGRAM

CONSULT-II Reference Value in Data Monitor Mode
Specification data are reference values.

ECM Terminals and Reference Value
Specification data are reference values and are measured between each terminal and 48 (ECM ground).

ON BOARD DIAGNOSIS LOGIC
Malfunction is detected when vacuum cut valve bypass valve does not operate properly.

Possible Cause
- Vacuum cut valve bypass valve
- Vacuum cut valve
- Bypass hoses for clogging
- EVAP control system pressure sensor and circuit
- EVAP canister vent control valve
- Hose between fuel tank and vacuum cut valve clogged
- Hose between vacuum cut valve and EVAP canister clogged
- EVAP canister
- EVAP purge port of fuel tank for clogging

DTC CONFIRMATION PROCEDURE

CAUTION: Always drive vehicle at a safe speed.

NOTE: If "DTC Confirmation Procedure" has been previously conducted, always turn ignition switch "OFF" and wait at least 5 seconds before conducting the next test

TESTING CONDITION: Always perform test at a temperature of 5 to 30 °C (41 to 86 °F).

With CONSULT-II
1. Turn ignition switch "ON".
2. Start engine and warm it up to normal operating temperature.
3. Turn ignition switch "OFF" and wait at least 5 seconds.
4. Start engine and let it idle for at least 70 seconds.
5. Select "VC CUT/V BP/V P1491" of "EVAPORATIVE SYSTEM" in "DTC WORK SUPPORT" mode with CONSULT-II.
6. Touch "START".

7. When the following conditions are met, "TESTING" will be displayed on the CONSULT-II screen. Maintain the conditions continuously until "TESTING" changes to "COMPLETED". (It will take at least 30 seconds.)
If "TESTING" is not displayed after 5 minutes, retry from step 3.
8. Make sure that "OK" is displayed after touching "SELF-DIAG RESULTS". If "NG" is displayed, refer to "Diagnostic Procedure".

Overall Function Check
Use this procedure to check the overall function of vacuum cut valve bypass valve. During this check, the 1st trip DTC might not be confirmed.

With Generic Scan Tool
1. Remove vacuum cut valve and vacuum cut valve bypass valve as an assembly.
2. Apply vacuum to port A and check that there is no suction from port B.
3. Apply vacuum to port B and check that there is suction from port A.
4. Blow air in port B and check that there is a resistance to flow out of port A.
5. Supply battery voltage to the terminal.
6. Blow air in port A and check that air flows freely out of port B.
7. Blow air in port B and check that air flows freely out of port A.
8. If NG, go to "Diagnostic Procedure".