Toyota Tacoma P0505: Idle Air Control System- Malfunction

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

P0505:  Idle Air Control System:  Malfunction

P0505 usually occurs due to a stuck idle valve, a blocked idle valve control valve, or an unattended vacuum leak.  However, there are other possible causes.  Although, they aren’t as prevalent.

P0505 Toyota Tacoma


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

P0505 Symptoms:  Toyota Tacoma

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
  • Low idle speed 


Tacoma 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.

Toyota Tacoma 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.

It is possible for the IAC to become stuck or dirty.  The IAC valve may require a replacement or cleaning may suffice.  Here’s a great Video from YouTube How to clean an idle air control valve  

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

You can code your Tacoma by leaking around the throttle body and intake manifolds.  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.

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.  This problem is usually solved by cleaning the area around the throttle blades.



You will be able to diagnose P0505 on your Tacoma.  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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