P0506: Idle Air Control System RPM Lower Than Expected
5 vehicles · 5 makes · $20-$900 repair
Most Reported On
P0506 is an OBD-II diagnostic trouble code meaning “Idle Air Control System RPM Lower Than Expected.” This code means the engine computer detected that the engine's idle speed is lower than the target idle RPM it commanded. The PCM controls idle speed through the idle air control valve or electronic throttle and sets this code when the actual idle drops below expected. A low or rough idle can cause stalling, hesitation, and reduced drivability. This code is most commonly reported on 2017-2020 Ford Transit Connect, 1996-2005 Honda Civic (CX, DX, LX, EX, HX), and 1993-1999 Mazda 626 (DX, LX, ES, GT), plus 2 other vehicles, with repair costs ranging from $20 to $900.
Common Causes
Typical Repair Cost
Based on 5 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0506, 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
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Vehicles Affected (5)
FAQ
What does P0506 mean?
P0506 stands for "Idle Air Control System RPM Lower Than Expected." This code means the engine computer detected that the engine's idle speed is lower than the target idle RPM it commanded. The PCM controls idle speed through the idle air control valve or electronic throttle and sets this code when the actual idle drops below expected. A low or rough idle can cause stalling, hesitation, and reduced drivability.
What are the most common causes of P0506?
The most common causes of P0506 are: Vacuum leak in intake or hoses, Dirty or carbon-clogged throttle body, Faulty idle air control (IAC) valve, Dirty or failing mass airflow sensor, Clogged PCV system or EGR sticking open, Worn or dirty fuel injectors, Excessive engine load from accessories. The specific cause varies by vehicle.
How much does it cost to fix P0506?
Repair costs for P0506 range from $20 to $900, depending on the vehicle and root cause.
Which vehicles are affected by P0506?
Au7o has documented P0506 across 5 vehicle models from 5 manufacturers: Chevrolet, Ford, Honda, Mazda, Toyota.
Sources (9)
- ForumReddit r/MechanicAdvice Thread Discussing 2018 Ford Transit Connect Stalling and PCM Update
- 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
- articleP0234 on 2018-2022 Chevrolet Equinox: Turbo Overboost Causes & Fixes
- ForumTurbo failure - GMC Terrain, Equinox, and SRX Forum
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.