AutoZone 2005 Chevrolet Truck Equinox 2WD 3.4L SFI 6cyl | Repair Guides | Driveability & Emissions Controls | Electronic Engine Controls | Idle Air Control (iac) Valve | AutoZone.com

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    Toyota Previa 1991-1997 Repair Information

    Idle Air Control (IAC) Valve

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    OPERATION



    See Figure 1

    The rotary solenoid type IAC valve is located on the throttle body and intake air bypassing the throttle valve is directed to the IAC valve through a hose. In this way the intake air volume bypassing the throttle valve is regulated, controlling the engine speed. The ECM operates only the IAC valve to perform idle-up and provide feedback for the target idling speed and a Vacuum Switching Valve (VSV) for idle-up control is also added for models with air conditioning.



    Click image to see an enlarged view

    Fig. Fig. 1: The Idle Air Control (IAC) valve is secured to the side of the throttle body

    TESTING



    2TZ-FE Engine

    See Figures 2 through 5

    1. Disconnect the IAC valve wiring.
    2.  
    3. Using an ohmmeter, measure the resistance between terminals +B and the other terminals (ISC1 and ISC2 or ISCC and ISSC, depending on the year of the van).
    4.  



    Click image to see an enlarged view

    Fig. Fig. 2: Use an ohmmeter to measure the resistance between the terminals of the IAC valve-ISC1 and ISC2 type



    Click image to see an enlarged view

    Fig. Fig. 3: Use an ohmmeter to measure the resistance between the terminals of the IAC valve-2TZ-FE engine-ISCC and ISSC type

    1. Resistance should be between 18.8-22.8 ohms.
    2.  
    3. If the resistance is not within specifications, replace the IAC valve.
    4.  
    5. To check the operation of the IAC valve, the engine should be at normal operating temperature and the transmission in Neutral.
    6.  
    7. Using a jumper wire, connect terminals TE1 and E1 of the DLC1.
    8.  



    Click image to see an enlarged view

    Fig. Fig. 4: A jumper wire is placed on these two terminals of the DLC1 to test the IAC valve operation-ISC1 and ISC2 type



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    Fig. Fig. 5: A jumper wire is placed on these two terminals of the DLC1 to test the IAC valve operation-ISCC and ISSC type

    1. After the engine rpm is kept at 1000-1200 for about 5 seconds, check that the rpm drops about 200 rpm.
    2.  
    3. If the rpm operation is not as specified, check the IAC valve, wiring and engine ECM.
    4.  
    5. Remove the jumper wire form the DLC1.
    6.  

    2TZ-FZE Engine

    See Figures 5 and 6

    1. Disconnect the IAC valve wiring.
    2.  
    3. Using an ohmmeter, measure the resistance between terminals +B and the other terminals RSC and RSO.
    4.  



    Click image to see an enlarged view

    Fig. Fig. 6: Use an ohmmeter to measure the resistance between the terminals of the IAC valve-2TZ-FZE engine

    1. Resistance should be between 17.0-24.5 ohms cold and 21.5-28.5 ohms hot.
    2.  
    3. If the resistance is not within specifications, replace the IAC valve.
    4.  
    5. To check the operation of the IAC valve, the engine should be at normal operating temperature and the transmission in Neutral.
    6.  
    7. Using a jumper wire, connect terminals TE1 and E1 of the DLC1.
    8.  
    9. After the engine rpm is kept at 1000-1200 for about 5 seconds, check that the rpm drops about 200 rpm.
    10.  
    11. If the rpm operation is not as specified, check the IAC valve, wiring and engine ECM.
    12.  
    13. Remove the jumper wire form the DLC1.
    14.  

    REMOVAL & INSTALLATION



    See Figures 7 and 8

    1. Remove the throttle body.
    2.  
    3. Remove the 4 screws to extract the IAC valve from the throttle body. Discard the gasket.
    4.  



    Click image to see an enlarged view

    Fig. Fig. 7: The IAC has a wiring harness attached to it

    To install:
    1. Install a new gasket on the throttle body and place the IAC valve into position.
    2.  
    3. Secure the IAC valve on the throttle body.
    4.  



    Click image to see an enlarged view

    Fig. Fig. 8: Remove these four bolts to extract the IAC valve from the throttle body

     
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