P0505 Honda Error Code: What Does It Mean?

It can be challenging to know what each code means every time you get one for your car. However, it can’t hurt to know the basic and most frequent ones, whether it’s dire or not. 

One such issue code is the p0505 Honda which indicates issues with the idle air control valve (IACV) system. It’s a universal code and applies in the same way to all other types of vehicles and not just Honda. A malfunctioning IACV can cause critical performance issues to your car. 

Continue reading to know what it means and what steps you should take next when you get this code. 

P0505 Honda

What Does It Mean?

A p0505 code usually indicates that there is an idle control system malfunction and deals with the idle air control valve (IACV) system. This mechanism regulates engine idle speed to a predetermined level. 

The amount of air that escapes the throttle valve through the IACV and Auxiliary Air Control (AAC) valve is finely adjusted to control idle speed. This code trigger usually means that there is likely a jammed or clogged air control valve or there is a vacuum leakage that is affecting its performance. Some people believe, it’s related to P0420 code in Honda models, of which i found no truth.

What Are The Symptoms?

This P0505 code, when triggered, will only let you know that there is a malfunction with the idle air control valve, but nothing more than that. The code is merely a clue that there is something wrong, but you have to figure out what the issue with the idle is. You have to troubleshoot before making a replacement if needed.

Therefore, it is suggested to look out for these simple symptoms before taking your car to a store or mechanic:

Engine Light ON/Service Engine Soon Warning Light: 

An engine light signal can be caused by several reasons, one of them being a malfunction with the idle air control valve system. Frequent engine stalling while idling or after ignition is probably an indication. Get your car checked to confirm suspicions. 

Erratic and rough Idling behaviors: 

The diel air control valve affects the idle RPM as well; hence it can naturally cause erratic behavior when there is a malfunction of the IACV. 

With a faulty IACV, you may observe the RPM jumping up to higher or acting more unpredictably than usual when idling. This is a clear indication of getting your engine checked immediately! 

Frequent Engine Stalling:

A faulty idle air control valve will restrict the engine’s airflow. This enables stalling of the car as not enough air is reaching the car’s engine. The intensity of engine stalling can range from sporadic stalling or stalling shortly after ignition and as a result, affect overall performance. 

What Are the Causes Triggering the P0505 Code?

There are generally 3 main reasons that can cause the p0505 code to trigger, and they are: 

Issues with the Idle Air Control Valve (IACV): 

The major function of the idle air control valve is to keep your engine’s idle speed under control. It accomplishes this by allowing just enough air to regulate the idle speed properly. 

Therefore, it’s crucial for the IACV to operate properly. The valve can either become clogged by dirt or jammed, which is likely to throw the p505 code.  

Vacuum Leak:

While the idle air control valve is frequently the source of a p0505 code trigger, however, looking for a vacuum leak is a good place to start diagnosing as well. Vacuum tubes around the IACV can become cracked or rotted quite frequently than it seems. 

In addition, leakage in the inlet manifold and around the throttle body might also cause this code to appear on your car. Therefore, look for vacuum leaks before thinking of replacing your idle air control valve entirely. 

Buildup of Carbon:

A dirty throttle body due to a buildup of carbon can alter the amount of air that can enter the engine. When this happens, the engine may frequently stall for a split second before recovering when you slow down. The reason why it throws the p0505 code is as a result of the engine’s inability to adapt to the problem quickly. 

How To Fix the P0505 Code?

How To Fix the P0505 Code

Cleaning or replacing a fault IACV: 

Another probable reason is that a dirty or stuck idle air control valve is likely to be the most probable cause for the P0505 code. In such cases, a clogged IACV can easily be cleaned, which will get rid of the P0505 problem for you. 

However, if there is a use with the IACV itself or it is quite old, a replacement may be required, but fear not, as a new idle air control valve is quite affordable as well. 

Repairing Vacuum Leaks:

Vacuum tube leaks can occur quite frequently around the IACV. They can either be dry rotted or cracked, which is likely disrupting the airflow. In such cases, repairing them may solve the problem, or a replacement may be required, depending on the conditions. This can also help with the P0134 Honda code.

Cleaning Carbon Buildups: 

Carbon buildup around the throttle blades and IACV passages is another common reason for triggering the p0505 code. Examining and cleaning carbon-blocked channels around the IAC regions is likely to fix the issue at hand and will enable air to circulate properly. 

How To Diagnose The P0505 Code? 

Diagnosing the p0505 code is quite simple, and there are several methods that you can check, and they are as follows: 

  • Analyzing whether the engine idles stay within the set standards on the road as well as in and out of gear. 
  • Check for vacuum leaks around the IACV. 
  • Inspect the engine for carbon buildup on the throttle plates and the entrance of the IACV. 
  • Remove the IACV to check if the engine’s base idle meets the standards.

How Serious Is the P0505 Code?

The severity of the code depends on the condition of the IACV, and vacuum tubes are, and whether replacements are needed or not. These are the issues that can be a cause of the p0505 code, which might add more cost to the issues if not addressed soon. 

A malfunctioning IACV can cause the car to idle roughly or incorrectly, which may add more stress to the engine’s performance. This is likely to cause more damage in the long run. 

If the code is caused by a vacuum leak, then it can cause the car to idle roughly and, in addition, lead to poor fuel efficiency, which will add more costs. 

A vehicle is likely to fail the emission test when the Check Engine light is on, which will be illuminated when a p0505 code is thrown. 

What’s The Cost to Fix It?

Just like any other diagnosis and repairs of such types of codes, the cost varies substantially based on multiple factors. For example, a large part of it will depend on the labor rates, which again is dependent on the region, vehicle model as well as engine types. 

The rates in auto repair shops will be hourly based, which, on average, range from $75 to $150. 


In most cases, the p0505 Honda code is triggered by either a vacuum leak or an issue with the IACV. However, with that being said, this code doesn’t always mean that you need a replacement for your IACV. Get it checked by a professional first to determine the root cause of the problem. 

It’s recommended to get the issue addressed and checked as soon as possible to avoid racking up more costs. 

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