P0505: Idle Air Control System Malfunction
8 vehicles · 6 makes · $20-$700 repair
Most Reported On
P0505 is an OBD-II diagnostic trouble code meaning “Idle Air Control System Malfunction.” P0505 indicates a malfunction in the idle air control (IAC) system, which manages how much air bypasses the throttle plate to keep the engine idling smoothly at the correct RPM. On older systems this is a dedicated IAC valve/motor; the computer uses it to raise idle for cold starts, A/C load, or accessory load. When the system can't maintain the target idle, you may get a high or low idle, surging, rough idle, or stalling — especially at stops or when cold. The cause is usually a dirty or failed IAC valve, but vacuum leaks and electrical faults are common too. This code is most commonly reported on 2009-2014 Nissan Cube, 2010-2015 Volvo XC60 (3.2), and 1998-2000 Volvo S70, plus 5 other vehicles, with repair costs ranging from $20 to $700.
Common Causes
Typical Repair Cost
Based on 9 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0505, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Vehicles Affected (8)
FAQ
What does P0505 mean?
P0505 stands for "Idle Air Control System Malfunction." P0505 indicates a malfunction in the idle air control (IAC) system, which manages how much air bypasses the throttle plate to keep the engine idling smoothly at the correct RPM. On older systems this is a dedicated IAC valve/motor; the computer uses it to raise idle for cold starts, A/C load, or accessory load. When the system can't maintain the target idle, you may get a high or low idle, surging, rough idle, or stalling — especially at stops or when cold. The cause is usually a dirty or failed IAC valve, but vacuum leaks and electrical faults are common too.
What are the most common causes of P0505?
The most common causes of P0505 are: Dirty or carbon-clogged idle air control valve, Failed IAC valve motor or stuck pintle, Vacuum leak in the intake system, Dirty throttle body or sticking throttle plate, Wiring or connector fault in the IAC circuit, Faulty PCV system causing unmetered air, PCM/ECM control fault. The specific cause varies by vehicle.
How much does it cost to fix P0505?
Repair costs for P0505 range from $20 to $700, depending on the vehicle and root cause.
Which vehicles are affected by P0505?
Au7o has documented P0505 across 8 vehicle models from 6 manufacturers: Ford, Honda, Mazda, Nissan, Toyota, Volvo.
Sources (9)
- ForumSwedeSpeed Forum - XC60/SI6 PCV Oil Trap Failure, Whistling Noise and Oil Consumption
- ForumFord Ranger Known Problem Areas - The Ranger Station
- videoYouTube - EricTheCarGuy: How to Clean and Replace Idle Air Control Valve on Ford Triton Engines
- articleCivic Idle Air Control Valves - AutoZone
- articleHonda Civic Idle Air Control (IAC) Valve Replacement - 1A Auto
- articleMazda 626 Rough and Unsteady Idle - troubleshooting IAC and intake gasket
- ForumIntake Manifold Vacuum Leak Causing Rough Idle: Mazda 626
- ForumHigh idle and P0505. IAC seems functional — Toyota-4Runner.org (3rd Gen)
- articleP0505 on 1995-2004 Toyota 3.4L V6: Idle Control System Causes and Fixes — Go-Parts
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.