P0506Generic code

P0506 Code: Idle Control System RPM Lower Than Expected

The P0506 code means the engine is idling below what the computer asks for. The most frequent cause is a dirty throttle body or a stuck idle valve. Cleaning fixes it very often, and many vehicles then need an idle relearn.

Severity
Medium
Can I keep driving?
Yes, but with caution
Estimated cost
$0 to $300
Difficulty
Easy
System
Idle and Speed Control
Applies to
All OBD2 vehicles

Common in: Chevrolet

Updated Reviewed by Renzo Chacca

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What the P0506 code means

The computer sets a target idle speed based on temperature and loads. If the real rpm stays below it for a period of time, even though the computer opens the idle valve or the throttle all the way, it stores the P0506 code.

Almost always the engine is short of air. Carbon on the throttle or on the IAC valve reduces the passage, or the air filter is badly clogged. It can also happen from an excessive load (a stiff A/C compressor or a dragging alternator).

If there are also misfires or fuel mixture codes, fix those first, because an engine that runs poorly cannot hold its idle.

After you clean the throttle body, many vehicles with an electronic throttle need an idle relearn. Without it, the computer keeps using the correction it learned for a dirty throttle, and the idle stays high or unstable for days. Some manufacturers do it with a scan tool and others with a sequence of key and idle steps (on a Nissan, for example, the idle air volume learn procedure).

P0506 code symptoms

  • Low idle and vibration.
  • The engine stalls when you stop.
  • Idle that drops when the A/C comes on.

Likely causes of the P0506 code

  1. Dirty throttle body or IAC valve. The most frequent cause.
  2. Clogged air filter, which cuts the air available at idle.
  3. Excessive load from the A/C compressor or the alternator.
  4. Idle relearn lost after disconnecting the battery.
  5. Misfires. An engine that misfires cannot hold its speed.

How to diagnose the P0506 code step by step

  1. Compare desired and actual idle on the scan tool.
  2. Clean the throttle body.
  3. Perform the idle relearn.
  4. Check the engine loads. Turn off the A/C and see whether it improves.
  5. Check for vacuum leaks. They usually raise the idle, but a large leak can upset the control.

How to fix the P0506 code

  • Clean the throttle body and the IAC valve.
  • Perform the idle relearn.
  • Repair the cause of the excessive load.
  • Clear the codes and verify.

Technical reference data

  • Typical warm idle: 650 to 850 rpm.
  • Approximate values only: check the manufacturer data for your vehicle.

Brand-specific notes

This code is very frequent on several makes with an electronic throttle that gets dirty.

P0506 on Ford

Very frequent on Ford vehicles with a dirty electronic throttle.

P0506 on Nissan

Very frequent on Nissan vehicles with a dirty electronic throttle. After cleaning, run the idle air volume learn procedure.

P0506 on Toyota

Very frequent on Toyota vehicles with a dirty electronic throttle.

Frequently asked questions about P0506

Can I drive with a P0506 code?
Yes, with caution. A P0506 code can let the engine stall when you stop, which is a hazard at an intersection.
Does cleaning fix it?
Very often.
What is an idle relearn?
A procedure that lets the computer learn the throttle position again after cleaning or after the battery has been disconnected.
How much does it cost to fix P0506?
From $0 if you clean it yourself up to about $300, depending on whether it is a cleaning job or a part.
What does the P0506 code mean?
It is a generic OBD2 code that means the engine idles below the speed the computer requests, even with the idle valve or throttle opened all the way.
What is the most common cause of P0506?
A dirty throttle body or IAC valve. A clogged air filter or an excessive load come next.

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