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DTC P0505: Idle Control System Malfunction

NOTE: If DTC P1519  is also set, trouble shoot that DTC before DTC P0505.
  1. Start engine and hold at 3000 RPM with no loads and transmission in Park or Neutral, until cooling fan comes on. Let engine idle. Using scan tool, check engine speed at idle with no loads (headlights, blower motor, rear defogger, radiator cooling fan, and A/C are all off). If idle speed is 700-800 RPM, problem is intermittent, system is okay at this time. If idle speed is 700 RPM or less, go to next step. If idle speed is not 700 RPM or less, go to step 3).
  2. Disconnect Idle Air Control (IAC) valve 3-pin connector. If engine speed does not increase, replace IAC valve. If engine speed increases, adjust base idle speed. See the ADJUSTMENTS article. If base idle speed does not adjust to specification, clean throttle body and ports.
  3. Remove intake air duct from throttle body. Place your finger over upper port in throat of throttle body. If engine idle speed decreases, adjust idle speed. See the ADJUSTMENTS article. If idle speed can not be adjusted to specification, replace IAC valve. If engine speed does not decrease, check for vacuum leaks. Ensure throttle valve is fully closed. Repair as necessary.
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