P0519 moderate

Idle Air Control System Performance

The P0519 code means the vehicle's onboard diagnostic system has detected: Idle Air Control System Performance. This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: moderate
Estimated cost: $30 - $300 (parts and labor)

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Common Symptoms

Check Engine Light on
Idle speed higher or lower than specification
Rough or unstable idle
Stalling when coming to a stop

Probable Causes (Ranked by Likelihood)

Carbon buildup in throttle body or IAC passages Very High
Vacuum leak affecting idle air metering High
Worn or sticking IAC valve Moderate
Throttle body requires relearn after cleaning or battery disconnect Moderate

Step-by-Step Diagnostic Procedure

Check idle speed against manufacturer specification; note whether it is high, low, or erratic
Inspect throttle body and IAC passages for carbon buildup; clean if excessive
Check for vacuum leaks using a smoke machine or spray method
Perform an idle relearn procedure after any throttle body cleaning or battery disconnection

Frequently Asked Questions

What is the idle air control system?

The idle air control system manages engine idle speed by regulating airflow through the throttle body when the throttle plate is closed. On newer vehicles with electronic throttle, the ECM controls idle by slightly opening the throttle plate.

Do I need to perform an idle relearn?

Yes. After cleaning the throttle body, replacing the IAC valve, or disconnecting the battery, many vehicles require an idle relearn procedure. This allows the ECM to recalibrate its idle control parameters. The procedure varies by manufacturer.

Can a dirty throttle body cause P0519?

Yes. Carbon and oil residue in the throttle body can restrict the idle air passage, causing the ECM to report that idle control performance is outside acceptable parameters. Cleaning the throttle body is often the first repair step.