P0506 OBD-II Trouble Code: Idle Control System RPM lower Than Expected

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Cost of diagnosing the P0506 code

P0506 is a diagnostic trouble code (DTC) for "Idle Control System RPM lower Than Expected". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

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P0506 code definition

When the P0506 diagnostic trouble code is stored by the Powertrain Control Module (PCM), it is an indication that the revolutions per minute (RPM) of the idle control system is lower than expected.

Related diagnostic trouble codes:

  • P0505 OBD-II Trouble Code: IAC (Idle Air Control) System Malfunction
  • P0507 OBD-II Trouble Code: Idle Air Control System RPM Higher Than Expected

What the P0506 code means

Today, most vehicles have electronic throttle control. The throttle is controlled by sensors and the PCM and the engine idle speed is controlled by the idle air control system.

In addition to the engine idle speed, the Idle Air Control System also controls the air conditioner, heater blower, and windshield wipers.

When a vehicle is idling, the engine idle speed should remain between 750 RPM and 1000 RPM. If the engine idle speed drops lower than 750 RPM, the PCM will store the P0506 diagnostic trouble code.

What causes the P0506 code?

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

What are the symptoms of the P0506 code?

  • Check Engine Light on
  • Low engine idle speed
  • Rough engine idle
  • Unpredictable idling
  • Engine stalls when car comes to a stop

How does a mechanic diagnose the P0506 code?

  • Uses an OBD-II scanner to get all of the trouble codes that are stored by the PCM.

  • Views freeze frame data to see what the conditions of the engine were when the P0506 diagnostic trouble code was set.

  • Clears the code(s) and performs a test drive to see if the code comes back.

  • On the OBD-II scanner, they will view the data stream and compare the current engine idle RPM with the manufacturer’s pre-set idle RPM levels.

  • Tests the engine idle revolutions per minute by turning on the air conditioner and heater blower motor. They will place various loads on the engine during this stage of the diagnostic process to find out if the PCM is able to maintain a normal engine idle speed.

  • Inspects the throttle body for vacuum leaks and high carbon build up. If there is high carbon build up, the throttle body will need to be cleaned.

  • Views live data on the OBD-II scanner to see if the idle air control system and PCM is working properly.

Common mistakes when diagnosing the P0506 code

Sometimes, there are other diagnostic trouble codes that have been stored by the PCM in addition to the P0506 trouble code. These codes should also be checked to avoid a misdiagnoses. It is also important to check for vacuum leaks and carbon buildup in the throttle body air passages.

How serious is the P0506 code?

The P0506 diagnostic trouble code can cause a loss of power while driving, which could make driving conditions hazardous. For this reason, this code is regarded as serious. Diagnosis and repair should be complete as soon as possible.

What repairs can fix the P0506 code?

Additional comments for consideration regarding the P0506 code

Common causes of the P0506 diagnostic trouble code are vacuum leaks and dirty throttle body air passages. Therefore, it is important to inspect the throttle body plate and clean it, if necessary. It is also important to view live data to check engine idle RPM, idle air control system, and PCM functionality.

Need help with a P0506 code?

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