49 RPM - High Idle (Vacuum Leak)

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The vacuum lines include the MAP sensor junction, PCV hoses, PCV valve, brake booster hose, the fuel pressure regulator hose, throttle body, intake manifold gasket and throttle body minimum idle adjustment. Code 49 detects a leak in any of these lines which may cause the idle speed to rise above the control of the IAC system. Code 49 is detected when engine idle cannot be reduced by the IAC motor and the IAC is determined to be working.

Code Parameters

Code 49 will set if:

  • The engine is idling higher than desired RPM.
  • The IAC is working properly.

Diagnostic Aids

  • Inspect the hoses for cracks or splits.
  • If all the hoses and connections are good, inspect the manifold gasket and MAP sensor seal for leaks.
  • Check minimum idle speed.
  • A short to ground in one of the IAC circuits may cause a Code 49 to set.
  • Check PCV valve. Refer to Emissions Section.