P0506 — Idle Control System RPM Lower Than Expected
Moderate severityWhat it means
P0506 is stored when the engine control unit sees a fault involving the idle air control system. The idle control system regulates engine speed at idle by metering air around or through the throttle. Here the idle speed is dropping below target, so the engine may stumble or stall at a stop.
Common symptoms
- Low or stalling idle
- Idle too high, too low, or hunting
- Stalling at stops
- Slow return to idle
Likely causes
- Vacuum leak or heavy carbon in the idle-air passage
- Faulty idle-air or throttle-body control
- Carbon buildup in the throttle body or idle passage
- Faulty idle-air control valve
What to check first
- Clean the throttle body and check for vacuum leaks
- Clean the throttle body and idle passages
- Check for vacuum leaks and perform an idle relearn
Can you keep driving?
Usually drivable, but stalling at junctions is a safety concern — fix it soon.
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