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OBD II Fault Code

  • OBD II P0509

OBD-II Code Engine idle speed is higher than normal is defined as a Idle Air Control System Circuit High

The Idle Control System manages the engine idle speed. To raise or lower the engine Idle speed, the engine control module (PCM), opens or closes the Idle Air Control valve to allow more or less air into the engine. When the PCM cannot achieve the desired RPM, it will set code P0509.

Engine idle speed is higher than normal Symptoms

  • Engine idle speed is higher than normal
  • Engine stalls when coming to a stop

Common Problems That Trigger the P0509 Code

  • Clogged air filter
  • Idle Air Control (IAC) valve failure
  • Powertrain Control Module (PCM) failure
  • Vacuum leak
  • Wiring issue
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