Audi A5 P0505: Idle Air Control System- Malfunction

P0505 An OBDII Code that addresses the idle air control system within the Audi A5.  It’s a generic code, which means that it has the same meaning for the A5 as it would any other vehicle (A5 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.  Other causes can also be involved.  Although, they aren’t as prevalent.

P0505 Audi A5


Índice de Contenido
  1. P0505 Symptoms:  Audi A5
  2. A5 P0505 Causes
    1. Valve to control the idle airflow
    2. Vacuum Leak
    3. Carbon Buildup
  3. Conclusion

P0505 Symptoms:  Audi A5

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.

  • Engine service engine will soon be light
  • Don't be rough
  • Stalling
  • Very high idle speed 


A5 P0505 Causes

A vacuum leak, or problem with an idle air control valve, are the most common causes of P0505.  While replacing the idle air control valve seems like a good idea, it’s worth your time to check for a Leakage of vacuum first.

Audi A5 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.  This is done by making sure that the engine's idle speed is maintained at the correct level.

You can either get the IAC valve stuck or dirty.  The IAC valve may require a replacement or cleaning may suffice.  Here’s a great You Tube video Here are some tips on cleaning an idle valve.  

You may need to replace your idle air valve if you feel it is time. 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.

Leakages around the throttle body and intake manifold can cause your A5 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.  It is possible to fix this problem by checking the IAC inlet area for blocked passages.

It can cause the intake of air to be reduced if the throttle body becomes too dirty.  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.  This problem is usually solved by cleaning the area around the throttle blades.



You will be able to diagnose P0505 on your A5.  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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