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1. Remove the idle air control (IAC) valve connector. 2. Remove the IAC valve attaching screws (1). NOTE: If the IAC valve has been in service: DO NOT push or pull on the IAC valve pintle. The force required to move the pintle may damage the threads on the worm drive. Also, DO NOT soak the IAC valve in any liquid cleaner or solvent, as damage may result. 3. Remove the IAC valve assembly (2). ^ Clean the IAC valve O-ring sealing surface, the pintle valve seat, and the air passage. ^ The IAC valve may be cleaned. Use a shop towel or parts cleaning brush to remove any heavy deposits. ^ Any shiny spots on the pintle or seat are normal and do not indicate misalignment or a bent pintle shaft. ^ If the air passage have heavy deposits, remove the throttle body for a complete cleaning. ^ Inspect the IAC valve O-ring for cuts, cracks, or distortion. Replace the O-rings if necessary. ^ When installing a new IAC valve, be sure to replace the valve with an identical part. The IAC valve pintle shape and diameter are designed for a specific application. MEASUREMENT PROCEDURE This procedure is only for installing a new IAC valve. IMPORTANT: If installing a new IAC valve, replace the IAC valve with an identical part. The IAC valve pintle shape and diameter are designed for the specific application. Measure the distance between tip of the IAC valve pintle and the mounting flange. If the distance is more than 28 mm (1.1 in), use finger pressure to slowly retract the pintle. The force required to retract the pintle of a new valve will not cause damage to the valve. INSTALLATION PROCEDURE

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Refer to Engine Controls Schematics MAF, Secondary Air Injection Pump Bypass Solenoid, IAC and Secondary AIR Pump . Circuit Description The AIR pump is used on this vehicle to lower tail pipe emissions on start-up. The powertrain control module (PCM) grounds the AIR pump relay control circuit, which energizes the AIR pump. The PCM also grounds the AIR solenoid valve control circuit, which energizes the AIR solenoid valve. The AIR solenoid valve opens allowing manifold vacuum to open the AIR control valves. The PCM enables both control circuits when AIR system operation is desired. When the AIR system is active, the AIR pump forces fresh air into the exhaust stream in order to accelerate catalyst operation. The AIR control valves replace the conventional check valves. When the AIR system is inactive, the AIR control valves prevent air flow in either direction. DTC P0412 applies to the AIR solenoid control circuit. DTC P0418 applies to the AIR pump relay control circuit. DTC P0410 sets if an air flow problem is detected. The PCM will run two tests using the heated oxygen sensor (HO2S) voltage to diagnose the AIR system. Both tests have two parts. The passive test is performed during regular AIR pump operation. The passive test consists of the following: Passive Test Part 1 When the AIR system is enabled, the PCM monitors the HO2S voltage. If the HO2S voltage goes below a threshold, the PCM interprets this as an indication that the AIR system is operational. Passive Test Part 2 When the AIR system is disabled, the PCM monitors the HO2S voltage. The HO2S voltage should increase above a threshold and switch normally. If both of these tests indicate a pass, no further action is taken. If one of the above tests failed or is inconclusive, the diagnostic will proceed to test two. The active test is performed specifically for diagnostic purposes. Test two consists of the following: Active Test Part 1 During this test the PCM turns the AIR system on during closed loop operation. When the AIR system is activated, the PCM monitors the HO2S voltage. If the AIR system is operating properly, the HO2S voltage should go below a predetermined threshold. Active Test Part 2 The PCM turns the AIR system off. The HO2S voltage should return to above a rich threshold.

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Located on the throttle body, the Idle Speed Control (ISC) valve opens the air bypass passage when the solenoid is ON and closes it when the solenoid is “OFF.” The ECM turns the ISC solenoid ON and OFF at a constant cycle of 20 times per second. It controls the bypass air flow by making “ON” time one cycle shorter or longer depending on conditions. In this system, the ECM controls the ISC solenoid valve according to the signals from various sensors and switches to control the bypass air flow which plays the following three roles as required by certain circumstances. IDLE-UP AIR FLOW When head lights & other lights, heater fan, rear defogger (if equipped) or air conditioner (if equipped) are operating, and/or the automatic transmission is in a range other than PARK or NEUTRAL, and/or the vehicle is at high altitudes, higher than 8,200 ft or 2,500 m, the bypass air is supplied to stabilize the engine idle speed. How much air is supplied varies depending on the load. When head lights and other lights are ON, the idle speed rises only a little higher than the normal specified idle speed (920 rpm). AFTER START AIR FLOW When and after the engine is started, the bypass air is supplied to prevent the engine from stopping when the throttle opener is OFF and to improve the engine performance at its start. How much bypass air is supplied varies depending on the engine cooling water temperature and it decreases as time passes when engine is cool. When engine is hot and 15 seconds have passed after engine starts, a given amount of bypass air is supplied until either the idle switch is turned OFF from ON once or engine speed exceeds 1,500 rpm once. DASHPOT AIR FLOW A sudden change in the throttle valve opening (especially when decelerating) causes the air/fuel mixture ratio to change suddenly. To compensate for this condition, the bypass air flow will be increased or decreased depending on condition. By increasing or decreasing the air, the air/fuel mixture ratio is changed gradually and dashpot effect is obtained. The air is increased when throttle is opened and decreased when the throttle is closed.

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1. If equipped, turn the air suspension switch OFF. 2. Disconnect battery ground cable. 3. Raise and support the vehicle; refer to Section 100-02. 4. Drain transmission fluid and remove the transmission fluid pan and filter; refer to Transmission Fluid Drain and Refill in this section. 5. CAUTION: Do not pull on the plastic lead frame. This may cause damage to the connector ends. Carefully pry up on the locking tabs to disconnect the sensors. Disconnect the molded lead frame from the sensors. Disconnect the molded lead frame from the sensors. 1. Disconnect the shift solenoid SSA/SS1 and SSB/SS2. 2. Disconnect the torque converter clutch (TCC). 3. Disconnect the electronic pressure control (EPC) solenoid. 4. Disconnect the bulkhead inter connector. 6. Remove the shift solenoid and the torque converter clutch (TCC) solenoid. 1. Remove the bolts. 2. Remove the shift solenoid and the torque converter clutch (TCC) solenoid. 7. Remove the manual control valve detent lever spring (7A261) 1. Remove the bolt. 2. Remove the manual control valve detent lever spring 8. Remove the 23 valve body to case bolts. 9. Remove the main control valve body (7A100) Installation 1. NOTE: Make sure that the drive pin of the manual valve detent lever assembly engages the manual valve in the proper location prior to installing the bolts. Position the main control valve body gasket and main control valve body using the two alignment bolts as a guide. 2. NOTE: The main control valve body bolts will be tightened in later steps. Loosely install the bolts. 3. NOTE: The main control valve body bolts will be tightened in later steps. Loosely install the bolts. 4. Install the manual control valve detent lever spring. 1. Position the manual control valve detent lever spring. 2. Install the bolt.

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Removal NOTE: 5.0L shown, 4.0L SOHC and 4.0L (push rod) similar. 1. Disconnect the idle air control (IAC) valve electrical connector. 2. Remove the IAC valve. 1. Remove the two bolts. 2. Remove the IAC valve. Discard the gasket. Installation NOTE: Install a new IAC valve gasket. 1. Install the idle air control (IAC) valve. 1. Position the IAC valve. 2. Install the two bolts. 3. Connect the IAC electrical connector.