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Idle Air Control Valve: Corolla

  1. Start engine and warm engine to normal operating temperature. Ensure idle speed is within specification. See IDLE SPEED & MIXTURE in ON-VEHICLE ADJUSTMENTS - 4-CYLINDER article.
  2. Turn ignition off. Apply parking brake and place transaxle in Neutral. Ensure A/C is off. Install Jumper Wire (SST 09843-18020 or SST 09843-18040) between terminals TE1 and E1 on data link connector No. 1. See Fig 1. Data link connector No. 1 is located at driver's side of engine compartment, near strut tower.
  3. Start engine and note engine speed. Engine speed should increase to 900-1300 RPM for 5 seconds and then return to idle speed. If engine speed is as specified, turn ignition off and remove jumper wire. If engine speed is not as specified, turn ignition off and remove jumper wire. Go to next step.
  4. To test Idle Air Control (IAC) valve operation, remove IAC valve from throttle body. See THROTTLE BODY under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article. Check that valve on inside of IAC valve is half open. See Fig 2. Reinstall electrical connector on IAC valve.
  5. Disconnect electrical connector from Engine Coolant Temperature (ECT) sensor. ECT sensor is located on flywheel end of cylinder head and contains Dark Gray electrical connector with White and Brown wires.
  6. Turn ignition on. Check that valve on inside of IAC valve moves. Repeatedly disconnect and reconnect electrical connector for IAC valve several times while checking that valve on inside of IAC valve opens and closes. See Fig 2.
  7. Turn ignition off. Reinstall electrical connector on ECT sensor. If IAC valve operates as specified, wiring circuit, Engine Control Module (ECM) and IAC valve are okay. If IAC valve does not operate, check wiring circuit between ECM and IAC valve. ECM is located behind stereo on instrument panel, just in front of center console. For illustration of ECM location, see THEORY & OPERATION article. It may be necessary to remove bolts from ECM so electrical connectors can be accessed on ECM. See ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article. See WIRING DIAGRAMS article. If wiring circuit and ECM are okay, replace IAC valve.
    Fig 1: Installing Jumper Wire Between Data Link Connector No. 1 Terminals (Corolla)
    G98E11225Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    Fig 2: Testing Idle Air Control Valve Operation (Corolla)
    G98F11846Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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