Toyota Corolla P0505: Idle Air Control System- Malfunction

P0505 An OBDII Code that addresses the idle air control system within the Toyota Corolla.  It’s a generic code, which means that it has the same meaning for the Corolla as it would any other vehicle (Corolla or not).

P0505:  Idle Air Control System:  Malfunction

P0505 usually occurs due to a stuck idle valve or clogged idle valve.  However, there are other possible causes.  Although, they aren’t as prevalent.

P0505 Toyota Corolla


Índice de Contenido
  1. P0505 Symptoms:  Toyota Corolla
  2. Corolla P0505 Causes
    1. Valve for Idle Air Control
    2. Vacuum Leak
    3. Carbon Buildup
  3. Conclusion

P0505 Symptoms:  Toyota Corolla

This particular trouble code lets you know that there is something wrong with the idle air control system, but that’s about it.  These symptoms could be different.

These are the top symptoms of P0505.

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


Corolla P0505 Causes

Most commonly, P0505 will be due to a vacuum leakage or a problem in the idle air control 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.

Toyota Corolla P0505 Diagnosis

Valve for Idle Air Control

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 Video from YouTube 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.  It may be necessary to replace them if they appear cracked or dry-rotted.

Leakages around the throttle body and intake manifold can cause your Corolla's code to be thrown.  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.  You can even throw P0505.  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.  This problem is usually solved by cleaning the area around the throttle blades.



You will be able to diagnose P0505 on your Corolla.  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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