P0506 Idle Air Control System RPM Lower Than Expected

P0506 indicates idle speed is lower than expected. The engine is idling below the control module's target even though the module is trying to manage it.

Code details

Generic OBD-II · P0

System: Speed / Idle
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not adjust mechanical throttle stops to raise idle unless service information requires it; modern systems usually need repair or relearn.

Symptoms of P0506

Unstable, high, or low idle, or stalling.
Erratic speedometer, cruise-control, or shift behaviour.
Check-engine light with a hesitation or surge.

Common causes of P0506

A dirty throttle body, idle-control valve, or throttle-position sensor.
A failing vehicle-speed or wheel-speed sensor, or its wiring.
Vacuum leaks or a related sensor forcing the idle/speed strategy.

Useful checks before replacing parts

Compare commanded idle, actual RPM, throttle angle, airflow, coolant temperature, and accessory load at warm idle.
Inspect throttle body deposits, intake restrictions, idle-control wiring, vacuum leaks, and learned idle values where applicable.
Look for companion air, fuel, misfire, throttle, or charging-system codes that can force low idle behavior.

Related OBD-II codes

These nearby speed / idle entries can help compare wording and pin down the fault area.