Idle Air Control Circuit
The P0511 code means the vehicle's onboard diagnostic system has detected: Idle Air Control Circuit. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- moderate
- Estimated cost
- $50 - $300 (parts and labor)
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What Are the Symptoms of P0511?
- Check Engine Light on
- Erratic or unstable idle speed
- Engine stalling at idle
- High idle speed
What Causes P0511? (Most Likely First)
- Faulty idle air control (IAC) valve Very High
- Carbon buildup in IAC valve or throttle body passages High
- Wiring fault in IAC circuit Moderate
- Vacuum leak affecting idle control Moderate
Can I Still Drive with P0511?
Short distances only. P0511 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What is the idle air control valve?
The IAC valve controls the amount of air bypassing the throttle plate at idle. By adjusting airflow, the ECM can maintain a stable idle speed under varying loads such as when the AC is turned on or the power steering pump is loaded.
Can cleaning the IAC valve fix P0511?
In many cases, yes. Carbon buildup is a common cause of IAC problems. Removing the valve and cleaning it with throttle body cleaner can restore proper operation. Also clean the passages in the throttle body.
Does my car have an IAC valve?
Many newer vehicles use electronic throttle control (drive-by-wire) instead of a separate IAC valve. These vehicles control idle speed directly through the throttle body motor. The IAC valve is common on older vehicles with cable-operated throttles.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose P0511?
-
Use a scan tool to monitor IAC valve commanded position vs actual idle speed
-
Remove and inspect the IAC valve for carbon buildup; clean with throttle body cleaner
-
Check IAC valve wiring and connector for damage, corrosion, or loose connections
-
Test IAC valve by commanding it through its range using a scan tool and listening for movement
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Which Vehicles Commonly Get P0511?
- 2005-2015 Toyota Corolla
- 2006-2016 Honda Civic
- 2008-2018 Chevrolet Silverado
- 2007-2017 Ford F-150
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