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Idle Air Control Valve: Tacoma

  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 transmission in Neutral. Install Jumper Wire (SST 09843-18020 or SST 09843-18040) between terminals No. 4 (CG) and No. 13 (TC) on data link connector No. 3. See Figure. Data link connector No. 3 is located behind driver's side of instrument panel. See Figure.
  3. Start engine and note engine speed. Engine speed should increase to 1000-1500 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 1. Reinstall electrical connector on IAC valve.
  5. Disconnect electrical connector from Engine Coolant Temperature (ECT) sensor. ECT sensor is located on coolant housing at rear of cylinder head and contains Dark Gray 2-pin electrical connector with Green/Red and Blue/Black 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 1.
  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 glove box. For illustration of ECM location, see THEORY & OPERATION article. See WIRING DIAGRAMS article. If wiring circuit and ECM are okay, replace IAC valve.
Fig 1: Testing Idle Air Control Valve Operation (Tacoma)
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