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DTC P0505 - Idle Control System

NOTE: If DTC P1508 is also stored, repair that DTC first.
  1. Start engine. Raise and hold engine speed at 3000 RPM with transmission in Park or Neutral, until cooling fan comes on. Let engine idle. Using scan tool, ensure throttle position is approximately 10 percent with throttle fully closed and engine coolant temperature is 194-205°F (90-96°C). If throttle position or engine coolant temperature are not within specification, repair faulty sensor circuit. Using scan tool, check engine speed. If engine speed is 650-750 RPM, system is okay at this time. Problem is intermittent.
  2. If engine speed is 650 RPM or less, go to step 4). If engine speed not is 650 RPM or less, turn ignition off. Remove air intake duct from throttle body. Start engine and allow it to idle. Place a finger on lower port in throttle body. If engine speed drops, check engine coolant level and for air in cooling system. If cooling system is okay, replace fast idle thermovalve.
  3. If engine speed does not drop, place a finger on upper port in throttle body. If engine speed does not drop, check for vacuum leaks and ensure throttle valve is completely closed. Repair as necessary. If idle speed drops, adjust idle speed to specification. See ADJUSTMENTS article. If idle speed will not adjust to specification, replace IAC valve.
  4. Disconnect IAC valve connector. If engine speed does not drop or engine does not stall, replace IAC valve. If engine speed drops or engine stalls, adjust base idle speed. See ADJUSTMENTS article. If engine speed does not adjust to specification, clean throttle body ports.
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