P0509 - Idle Control System Circuit High

The idle control circuit signal is higher than expected.

Code Overview

The idle control circuit signal is higher than expected.

Common Causes

• Failed sensor or idle control component
• Damaged wiring or connector
• Throttle body or switch issue

Diagnostic Steps

1. Inspect the related connector and harness
2. Compare live data to vehicle behavior
3. Check for mechanical sticking or adjustment problems

Likely Repairs & Cost Guides

Use test results to confirm the fault before pricing the repair.

Related OBD Codes

Browse the closest code-family pages when the same fault pattern often shows up nearby.

Next Steps

Move from the code to a diagnosis path, then into repair pricing once the fault is confirmed.