P0506: Idle Air Control System RPM Lower Than Expected

What does P0506 mean?

The ECM controls idle speed with an idle air control valve or, on newer cars, the electronic throttle. When actual idle stays below the target by more than an allowed amount, it stores P0506.

The references list a dirty throttle body, intake or exhaust restrictions, vacuum or PCV problems and internal engine problems as causes. A faulty PCM is possible but rare.

Common symptoms

• Check engine light on
• Low or rough idle
• Stalling, especially at stops
• Often no other symptoms

Common causes

The causes below are the ones commonly seen with P0506. The actual cause can vary by vehicle, engine and mileage, so treat this list as a starting point, not a diagnosis.

• A dirty or carbon coated throttle body or idle air control valve
• An intake or exhaust restriction
• A vacuum leak or faulty PCV valve
• Internal engine problems
• A faulty PCM (rare)

What to check with a scanner

• In Live data, compare actual idle rpm with desired idle rpm if your car reports it.
• Watch the idle with electrical loads on, such as lights and air conditioning.
• Note companion codes such as P0505 or P0507.
• Read freeze frame data for engine temperature when the code set.

How to read and clear P0506 with OBD Master Pro

1. Plug in your adapter. Connect a generic ELM327 (or ELM329) OBD2 adapter to the diagnostic port, usually under the dashboard on the driver's side. Bluetooth Classic, Bluetooth LE, Wi-Fi and USB OTG adapters are supported.
2. Switch the ignition on. Turn the key to ON or start the engine, depending on your car.
3. Connect in OBD Master Pro. Open the app, go to Connection and pick your adapter. Classic Bluetooth adapters connect from the Bluetooth tab, Bluetooth LE adapters from the BLE tab with no pairing needed. Use the generic OBD2 / EOBD profile or your car's brand profile.
4. Read the codes. Open the fault codes screen to see stored, pending and permanent codes. Confirm P0506 is listed and note any other codes, since they often explain the cause.
5. Check the details. Look at freeze frame data, Live data and, where your car supports it, Mode 06 test results (see the checks above).
6. Fix, then clear. After the repair, clear the codes to turn off the check engine light. Clearing also resets the emissions readiness monitors, so drive normally and check the readiness screen before any inspection. Permanent codes cannot be erased with a scan tool; they clear on their own once the car's self test passes.

Tip: you can also look up P0506 and other codes in the app's DTC search without connecting to a car. If your adapter will not connect, use Connection > Share connection log and email it to support. Many cheap ELM327 clones only handle basic engine OBD2, which is all you need for P0506.

When to see a mechanic

Get professional help if any of these apply:

• The engine stalls
• The throttle body needs cleaning and an idle relearn
• Internal engine problems are suspected

If you are unsure, a qualified technician can confirm the cause with tests such as smoke testing, pressure testing or scope readings. Clearing a code does not repair the fault.

Related trouble codes

See all OBD2 trouble code guides

Related guides

Check engine light on: what to do · How to read an OBD2 code (P, B, C, U) · Stored, pending and permanent codes and freeze frame · OBD2 readiness monitors explained · OBD2 glossary · OBD2 by car brand