Honda Accord P0505: Idle Air Control System- Malfunction

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

P0505:  Idle Air Control System:  Malfunction

P0505 usually occurs due to a stuck idle valve or a clogged idle valve.  Other causes can also be involved.  Although, they aren’t as prevalent.

P0505 Honda Accord


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

P0505 Symptoms:  Honda Accord

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
  • It is a rough idle
  • Stalling
  • Low idle speed 


Accord 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 Leakage of vacuum first.

Honda Accord 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.  The IAC valve may require a replacement or cleaning may suffice.  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.  Check the vacuum tubes surrounding the IAC.  You may need to replace the vacuum tubes around the IAC if they are cracked or dry rotted.

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


Carbon Buildup

It is possible for carbon to build up around the IAC 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.  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 Honda Accord.  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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