Ford Focus P0505 - Idle Air Control System - Malfunction

P0505 This OBDII code deals with the idle control system of the Ford Focus.  It’s a generic code, which means that it has the same meaning for the Focus as it would any other vehicle (Focus or not).

P0505:  Idle Air Control System:  Malfunction

P0505 triggers when there is either a stuck or clogged idle control valve or a vacuum leak.  However, there are other possible causes.  Although, they aren’t as prevalent.

P0505 Ford Focus


Índice de Contenido
  1. P0505 Symptoms:  Ford Focus
  2. Focus P0505 Causes
    1. Valve to control the idle airflow
    2. Vacuum Leak
    3. Carbon Buildup
  3. Conclusion

P0505 Symptoms:  Ford Focus

This particular trouble code lets you know that there is something wrong with the idle air control system, but that’s about it.  The symptoms may vary.

Below are some symptoms that P0505 is most commonly seen:

  • Soon, Service engine light
  • Don't be rough
  • Stalling
  • Very high idle speed 


Focus P0505 Causes

P0505 will usually indicate a vacuum leakage or a problem in the idle air valve.  While replacing the idle air control valve seems like a good idea, it’s worth your time to check for a Vacuum leak first.

Ford Focus P0505 Diagnosis

Valve to control the idle airflow

The idle air control valve’s primary job is to regulate the idle speed of your engine.  The idle air control valve regulates the engine's idle speed by controlling the amount of air that is allowed in.

You can either get the IAC valve stuck or dirty.  It may be necessary to replace it or clean it.  Here’s a great You Tube video Here are some tips on cleaning an idle valve.  

They are available if you decide that an idle valve control valve is needed. Very affordable.


Vacuum Leak

While the idle air control valve is often the cause of P0505, it’s a great idea to start diagnosing it by looking for a vacuum leak.  Examine the vacuum tubes near the IAC.  You may need to replace the vacuum tubes around the IAC if they are cracked or dry rotted.

You can code the Focus by leaking around your throttle body, intake leaks and other leaks.  Here’s a great article from Popular Mechanics on How to locate a vacuum leak.


Carbon Buildup

Carbon buildup can occur around the IAC's inlet.  The problem can be fixed by inspecting the IAC area for carbon-blocking passageways.

The throttle body can become too dirty to allow air to enter the engine.  This can cause P0505 to be thrown.  Often, when this is the case, you’ll feel the engine stall for a second before it recovers when slowing down.  

This happens because the engine can’t adjust to this problem fast enough.  It is possible to fix the problem by cleaning it from around the throttle blades.



You will be able to diagnose P0505 on your Focus.  Most of the time it’s a vacuum leak or the idle air control valve.  If you feel like there’s anything that you can add, please feel free to leave a comment below.

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