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P0506 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


The diagnostic trouble code P0506 stands for “Idle Speed Control System (ISC) RPM lower than expected”, an issue usually caused by defective idle air control motor and vacuum spills, which prompts loss of power in the engine’s performance.


The OBD II code P0506 typically occurs in cars with      Electronic Throttle Control (ETC) or cars with separate Idle Air Control (IAC) valves To control the idle speed, the IAC valve regulates the amount of air passing through the throttle body. Vehicles with ETC do not have a standard throttle cable or IAC. In this case, they depend on the electric motor to control the throttle and regulate the idle speed. The idling speed of the engine should remain between 800 – 1000 rpm. If the speed is lower than 800 RPM, the PCM will save the P0506 diagnostic trouble code


An OBD-II error code P0506 means that one or more of the following issues has occurred:

  • Defective idle air control motor
  • Dirty and/or defective throttle body
  • Vacuum leaks/loss
  • Problem with an internal engine component
  • Defective PCV valve
  • Faulty power steering pressure switch
  • Faulty PCM
  • Obstruction / Hindrance in the air intake or exhaust


Below mentioned are the common symptoms related to OBD error code P0506:

  • Check Engine Light on
  • Low engine idle speed
  • Unusual idling
  • Rough engine idle
  • Engine stalling when your car stops

Also read: How to Fix Low Oil Pressure at Idle?


For the correct diagnosis and solution of the error code P0506, you should follow the steps mentioned beneath

  • Use an OBD-II scanner to get the entirety of the trouble codes that are set aside by the PCM.
  • Observe freeze outline information to perceive the condition of the engine at the point, when the P0506 diagnostic trouble code was set.
  • Clear the code and perform a test drive to check whether the code returns. 
  • On the OBD-II scanner, you will see the information stream and compare the current engine idle RPM with the maker’s pre-set idle RPM levels.
  • Assess the engine idle revolutions per minute by switching on the air conditioner and radiator blower motor. It will put different loads on the engine during this phase of the diagnostic process . This helps in finding out whether the PCM is capable of maintaining a normal engine idle speed.
  • Examine the throttle body for vacuum leaks and high carbon development. In case there is high carbon build up, the throttle body needs to be cleaned immediately.
  • Watch live information on the OBD-II scanner to ensure that the idle air control system and PCM are working properly.    

Common mistakes

Sometimes, in addition to the P0506 trouble code, the PCM also retains other diagnostic trouble codes. These codes should also be verified to avoid misdiagnosis. It is important to check for vacuum leaks and carbon deposits in the throttle body air passage.

How serious is this?

The P0506 diagnostic trouble code will cause power to be cut off while driving, which could result in unsafe driving conditions. For this reason, this code is considered serious. Diagnosis and repair should be completed as quickly as possible.

If there are any driving problems, the vehicle should not be driven until it has been completely repaired by a professional auto mechanic.

What repairs can fix the code?

repair manuals

There are as many ways to fix this code as its causes. Of course, this requires a comprehensive diagnosis to determine the specific cause of the problem. Some common solutions for this code are:

  • Replace idle air control valve 
  • Clean dirty throttle body 
  • Repair any vacuum leaks 
  • Replace faulty throttle body
  • Replace idle air control motor
  • Replace or reprogram PCM 
  • Remove blockage in intake or exhaust 
  • Replace valve Faulty PCV 
  • Replace power steering pressure switch 
  • Diagnose and repair any other codes stored in PCM

Related codes

  • P0505 – Idle Control System Malfunction
  • P0507 – Idle Control System RPM Higher Than Expected
  • P0508 – Idle Air Control System Circuit Low
  • P0509 – Idle Air Control System Circuit High
  • P0171 – Fuel System Too Lean (Bank 1)
  • P0174 – Fuel System Too Lean (Bank 2)


The OBD-II scanner error code P0506 causes the engine to lose power, which could be dangerous especially if the vehicle is being driven or on road.. Therefore, it can cause serious problems. If not addressed for an extended period, it might cause significant damage to your engine, idle air control motor, PCM or other components of your vehicle. In latter cases, you may also find that an unfixed P0506 code can lead to the expensive replacements of engine components like throttle body, intake/exhaust valve, etc.

P0506 Code – What Does It Mean & How To Fix It