P0506 — Idle control system RPM lower than expected
What this code generally means, its most common causes, and how serious it is.
TYPE: GENERICSYSTEM: IDLE AND SPEED
What does the code P0506 mean?
More specific than P0505, this code means idle speed stays below the control module's target despite its adjustments — the engine runs slower than intended while stopped.
Common possible causes
A vacuum leak— can cause either a low or high idle depending on where it is.
A throttle body clogged enough to restrict airflow too much— prevents reaching the target speed.
An idle control valve stuck closed— limits the air available to hold idle speed.
General severity
Moderate — stalling risk when stopped
An idle that's too low can go as far as stalling the engine at a stop or a red light, especially with the AC or other accessories running. Worth checking fairly soon.
⚠️This is still a general severity for this code, not a diagnostic for your car. Only a real read of your codes, with your mileage and vehicle history, can tell what's really going on.
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Frequently asked questions
My engine sometimes stalls at red lights — is that related?›
That's a classic symptom of this code — an idle that's too low can go as far as stalling, especially with electrical accessories running.
Is this worse than a too-high idle (P0507)?›
A too-low idle carries a more direct stalling risk, while a too-high idle is mostly uncomfortable — both are worth checking.
Can I drive with this code?›
While moving, generally yes. The risk mainly shows up at complete stops.