P0505 - Idle Air Control System Malfunction

Idle control is not operating as expected.

Treat the code as the starting point: compare symptoms, likely causes, and repair paths before pricing parts or moving into an estimate.

Code Overview

Idle control is not operating as expected.

Common Causes

• Dirty throttle body or sticking throttle plate
• Idle air control valve failure on systems that use one
• Vacuum leak affecting idle control
• Idle relearn needed after battery or throttle service

Symptoms

• Idle speed hunts or will not stabilize
• Stalling or near-stall at stops
• Idle speed higher or lower than normal

Diagnostic Steps

1. Inspect the intake tract and vacuum hoses for leaks
2. Inspect and clean the throttle body if carbon buildup is present
3. Test the idle air control valve if the system uses one
4. Perform the idle relearn procedure if the vehicle requires it

Repair Difficulty

Moderate

General difficulty estimate for the most common repair path.

Likely Repairs & Cost Guides

Use symptoms, scan data, and quick checks to confirm the likely repair path before pricing parts. The estimator helps compare repair paths before replacing anything unnecessarily.

Related OBD Codes

Browse nearby code-family pages when the same fault pattern overlaps across systems, such as misfire, lean fuel trim, EVAP sealing, cooling, or charging faults.

Next Steps

Move from code lookup to diagnosis, then estimate the likely repair only after symptoms, causes, and checks point to the same path.