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    2003 BMW 540I 4.4L EFI DOHC 8cyl

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    1720 S RIDGEWOOD A
    (386) 427-1210

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    PT Cruiser 2006-2007

    Idle Air Control Valve

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    Operation



    The Powertrain Control Module (PCM) adjusts engine idle speed through the Idle Air Control (IAC) valve to compensate for engine load, coolant temperature, or barometric pressure changes. The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. The IAC valve regulates air flow through the bypass passage.

    The PCM controls engine idle speed by adjusting the position of the IAC valve. The adjustments are based on inputs the PCM receives. The inputs are from the Throttle Position Sensor (TPS), Crankshaft Position (CKP) sensor, Engine Coolant Temperature (ECT) sensor, Manifold Absolute Pressure (MAP) sensor, Vehicle Speed Sensor (VSS), and various switch operations (brake, park/neutral, Air Conditioning (A/C)).

    When the engine RPM is above idle speed, the IAC is used for the following functions:



    Off-idle dashpot
     
    Deceleration air flow control
     
    A/C compressor load control (also opens the passage slightly before the compressor is engaged so that the engine rpm does not dip down when the compressor engages)
     

    The target idle is determined by the following inputs:



    Gear position
     
    Engine Coolant Temperature (ECT) Sensor
     
    Battery voltage
     
    Ambient/Battery Temperature Sensor
     
    Vehicle Speed Sensor (VSS)
     
    Throttle Position Sensor (TPS)
     
    Manifold Absolute Pressure (MAP) Sensor
     

    Removal & Installation



    1. Before servicing the vehicle, refer to the Precautions Section.
    2.  
    3. Disconnect the negative cable from the battery.
    4.  
    5. Remove the electrical connector from the Idle Air Control (IAC) valve.
    6.  
    7. Remove the IAC valve mounting screws.
    8.  
    9. Remove the valve from the throttle body. Ensure the O-rings are removed with the valve.

      Click image to see an enlarged view

      Fig. Ensure the O-rings are removed with the Idle Air Control (IAC) valve

    10.  

    To install:

    When servicing throttle body components, always reassemble components with new O-rings and seals where applicable. Never use lubricants on O-rings or seals, damage may result. If assembly of component is difficult, a light coat of engine oil may be applied to the O-RINGS ONLY to aid assembly.

    1. The new IAC valve has a new O-ring installed on it.
    2.  
    3. Carefully place the IAC valve into the throttle body.
    4.  
    5. Install the mounting screw. Tighten the screw to 62 inch lbs. (7 Nm) torque.
    6.  
    7. Connect the electrical connector to the IAC valve.
    8.  
    9. Connect the negative cable to battery.
    10.  

    Testing




    NOTE
    If the engine will not idle, maintain an engine speed between 800 and 1,500 RPM.

    1. Start the engine. Allow the engine to idle. With the DRBIII®, read the Idle Air Control (IAC) Current. Is the IAC Current above 146 mA-
      1. If yes, go to Step 2.
      2.  
      3. If no, look for an intermittent condition symptom. Perform POWERTRAIN VERIFICATION TEST.
      4.  

    2.  
    3. Check the IAC valve/motor. Turn the ignition off. Disconnect the IAC valve harness connector. Remove the IAC Motor.
      NOTE
      Inspect the IAC air passages for restrictions and damage to the IAC valve.

      1. Measure the resistance across the IAC Motor pin terminals.
      2.  
      3. Is the resistance reading at 9.7 ohms (plus or minus 1.0 ohm)-

        If yes, go to Step 3
         
        If no, replace the IAC valve/motor. Perform the POWERTRAIN VERIFICATION TEST.

        Click image to see an enlarged view

        Fig. Idle Air Control (IAC) valve/motor connector pin view and schematics

         

      4.  

    4.  
    5. Check if the IAC return circuit is open (K961). Disconnect the C2 PCM harness connector.
      WARNING
      Do not probe the Powertrain Control Module (PCM) harness connectors. Probing the PCM harness connectors may damage the PCM terminals resulting in poor terminal-to-pin connection. Install Miller Special Tool #8815 to perform diagnosis.

      1. Measure the resistance of the (K961) IAC Return circuit from the IAC valve/motor harness connector to the appropriate terminal of special tool #8815.
      2.  
      3. Is the resistance below 5.0 ohms-

        If yes, go to Step 4
         
        If no, repair the open in the (K961) IAC Return circuit. Perform the POWERTRAIN VERIFICATION TEST.
         

      4.  

    6.  
    7. Check the IAC return circuit for a short to a ground. Measure the resistance between a ground and the (K961) IAC Return circuit in the IAC valve/motor harness connector. Is the resistance below 100 ohms-
      1. If yes, repair the short to ground in the (K961) IAC Return circuit. Perform the POWERTRAIN VERIFICATION TEST.
      2.  
      3. If no, go to Step 5.
      4.  

    8.  
    9. Check the IAC valve control circuit for an open condition. Measure the resistance of the (K61) IAC Control circuit from the IAC Motor harness connector to the appropriate terminal of the special tool #8815. Is the resistance below 5.0 ohms-
      1. If yes, go to Step 6.
      2.  
      3. If no, repair the open in the (K61) IAC Control circuit. Perform the POWERTRAIN VERIFICATION TEST.
      4.  

    10.  
    11. Check the IAC valve control circuit for a short to ground. Measure the resistance between a ground and the (K61) IAC Control circuit in the IAC Motor harness connector. Is the resistance below 100 ohms-
      1. If yes, repair the short to ground in the (K61) IAC Control circuit. Perform the POWERTRAIN VERIFICATION TEST.
      2.  
      3. If no, go to Step 7.
      4.  

    12.  
    13. Check for excessive resistance in the (K961) IAC signal circuit. Using a voltmeter, perform a voltage drop test.
      WARNING
      Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in a poor terminal-to-pin connection. Install the Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.

      1. Backprobe the (K961) IAC Signal circuit at the IAC harness connector and probe the appropriate terminal of the special tool #8815.
      2.  
      3. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.
        CAUTION
        When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

      4.  
      5. Start the engine and allow it to reach normal operating temperature.
      6.  
      7. Monitor the voltmeter. Is the voltage below 0.5 of a volt-

        If yes, go to Step 8
         
        If no, repair the excessive resistance in the (K961) IAC Signal circuit. Perform the POWERTRAIN VERIFICATION TEST.
         

      8.  

    14.  
    15. Check for excessive resistance in the (K61) IAC control circuit.
      1. Turn the ignition OFF.
      2.  
      3. Move the voltmeter leads to backprobe the (K61) IAC Control circuit at the IAC harness connector and to probe the appropriate terminal of the special tool #8815.
      4.  
      5. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.
        CAUTION
        When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

      6.  
      7. Start the engine and allow it to reach normal operating temperature.
      8.  
      9. Monitor the voltmeter. Is the voltage below 0.5 of a volt-

        If yes, go to Step 9
         
        If no, repair the excessive resistance in the (K61) IAC Control circuit. Perform the POWERTRAIN VERIFICATION TEST.
         

      10.  

    16.  
    17. Check the Powertrain Control Module (PCM).
      NOTE
      Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

      1. Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
      2.  
      3. Were there any problems found-

        If yes, repair as necessary. Perform the POWERTRAIN VERIFICATION TEST.
         
        If no, replace and program the PCM per Service Information. Perform the POWERTRAIN VERIFICATION TEST.
         

      4.  

    18.  

    Powertrain Verification Test

    NOTE
    After completing the Powertrain Verification Test, the Transmission Verification Test must be performed.


    NOTE
    If the Powertrain Control Module (PCM) has been replaced and the correct VIN and mileage have not been programmed, a DTC will set in the ABS Module, Airbag Module, and the SKIM/SKREEM.


    NOTE
    If the vehicle is equipped with a Sentry Key Remote Entry, Secret Key data must be updated. Using the scan tool, program the Secret Key information into the PCM using the PCM replaced function under the WCM menu.

    1. Before servicing the vehicle, refer to the Precautions Section.
    2.  
    3. Inspect the vehicle to make sure that all engine components are properly installed and connected. Reassemble and reconnect components as necessary.
    4.  
    5. Connect the scan tool to the data link connector.
    6.  
    7. Make sure the fuel tank has at least a quarter tank of fuel. Turn OFF all accessories.
    8.  
    9. After the ignition has been OFF for at least 10 seconds, restart the vehicle and run it for 2 minutes.
    10.  
    11. With the scan tool, monitor the appropriate pre-test enabling conditions until all conditions have been met.
    12.  
    13. Once the conditions have been met, switch the screen to the appropriate OBDII monitor. (There may be audible beeps when the monitor is running).
    14.  
    15. If the repaired OBDII trouble code has reset or was seen in the monitor while on the road test, the repair is not complete. Check for any related technical service bulletins or flash updates and return to diagnostic procedures.
    16.  
    17. If the conditions cannot be duplicated, erase all Diagnostic Trouble Codes (DTC-s) with the Scan tool.
    18.  
    19. If another DTC has set, begin diagnostic procedures to solve that particular DTC.
      1. Did the OBDII Monitor run successfully and has the Good Trip Counter changed to one or more-

        If yes, repair is complete.
         
        If no, check for any related Technical Service Bulletins and/or refer to the appropriate Diagnostic Procedure.
         

      2.  

    20.  

     
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