P0509
Idle Air Control System Circuit High
Moderateengine
Overview
The P0509 code indicates the engine control module has detected a idle air control system circuit high condition. This is an engine-related diagnostic trouble code that may indicate a mechanical or control issue affecting the engine's operation. Depending on the severity, this code may require immediate attention to prevent engine damage.
Symptoms
- Vehicle goes into reduced power mode
- Difficulty starting the engine
- Unusual engine noises (knocking, ticking)
- Engine overheating
Common Causes
- Carbon buildup in engine
- Faulty sensors providing incorrect data
- Timing chain/belt wear or failure
- Blown head gasket
Diagnosis Steps
- 1Connect an OBD-II scanner and read all stored trouble codes and freeze frame data
- 2Check engine oil level and condition; change if overdue
- 3Perform a compression and leak-down test
- 4Inspect related sensors and their wiring connections
- 5Listen for unusual engine noises indicating mechanical issues
Estimated Repair Cost
$200 — $3,000
Cost varies by vehicle, location, and repair shop. Includes parts and labor.
Commonly Affected Vehicles
Dodge ChargerBMW 3 SeriesHonda CivicKia Sorento
Related Codes
More Engine Codes
Frequently Asked Questions
Engine codes can range from minor sensor issues to critical mechanical failures. If you notice overheating, knocking, or significant power loss, stop driving and have the vehicle towed to a mechanic.