P0506 means Idle Air Control System RPM Lower Than Expected. Idle speed is lower than the computer is targeting, even after it has tried to raise it. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0506 means
Most vehicles built in the last two decades use electronic throttle control instead of a throttle cable: the accelerator pedal carries two or three position sensors, and the throttle body has a motor and two position sensors of its own. The computer compares the redundant sensors constantly, and any disagreement triggers reduced-power mode as a safety measure. Older engines with a throttle cable control idle with a separate idle air control valve.
P0506 symptoms
- Low or rough idle
- Stalling, especially with the AC on or in gear
- Vibration at idle
Common causes of P0506
- Carbon buildup in the throttle body or IAC passage
- Sticking IAC valve
- Restricted air intake
- Engine running poorly from misfires or low compression
How to diagnose P0506
- Clean the throttle body
- Inspect the air filter and intake
- Check for misfires and other codes
- Perform an idle relearn if required
Can you drive with P0506?
Usually yes, but stalling at intersections is a risk. Repair soon.
P0506 tips
If the idle drops and the engine stalls when the AC compressor engages, the computer cannot open the throttle or IAC enough to compensate, usually because of carbon. Cleaning plus an idle relearn fixes most P0506 codes.
Will P0506 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0506 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0505 | Idle Air Control System Malfunction |
| P0507 | Idle Air Control System RPM Higher Than Expected |
| P0300 | Random/Multiple Cylinder Misfire Detected |
Guides that help
- idle air control valve
- engine stalling
- throttle body
- engine misfire and flashing check engine light
- rough idle causes
When it is more than a sensor
Throttle and idle codes are fixed at the throttle body, the pedal, a sensor or a leak. If those check out and the engine still runs poorly, a compression test separates a control problem from a worn engine; compare engines by code on our engines page.
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