P0505 on Honda: How to Diagnose & Fix
Idle Air Control System Malfunction
1 Honda model · 1 documented issue · $50-$300 repair
P0505 on Honda by model: symptoms, diagnosis and fix
The idle air control valve (IACV) on the throttle body meters the air that bypasses the closed throttle at idle. On D-series Civics it fouls with carbon and the pintle sticks, so the ECU can no longer stabilize idle. Symptoms are a hunting/surging idle, abnormally high idle, or the engine dying when coming to a stop or cold. It is a common, inexpensive fix that owners search because the car stalls at intersections and feels erratic.
Common Symptoms
- Idle hunts up and down at stops
- Stalls when decelerating to a stop or when cold
- Abnormally high idle speed
- Rough shaking idle
- Stalls with A/C or electrical load applied
How to Fix
Remove and clean the IACV and throttle body with carburetor/throttle-body cleaner; replace the IACV if the pintle is stuck or the coil is out of spec. Reset idle relearn afterward. Clean the associated throttle-body ports (fast-idle thermovalve on older D-series).
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- 1996 Honda Civic genuine idle-control-valve catalogOEMHonda 16022-P2E-A51 / 36450-P2J-J01 / 16022-P2A-J01 by confi
Select exact VIN and do not transfer
- 2001-2005 Honda Civic genuine idle-control-valve catalogOEMHonda 16022-PLC-J01 automatic/CVT / 16022-PLC-003 5MT
Enter VIN because GX, Si and other engine/emissions branche
- Genuine Honda 16176-P2A-004 throttle-body gasketOEMHonda 16176-P2A-004
Do not buy for a cleaning procedure that does not detach the throt
- Genuine Honda 16176-PMR-A01 throttle-body gasketOEMHonda 16176-PMR-A01
Enter VIN because alternate engine/emissions branches exist; do not buy unless the procedure removes the
- CRC 05078 throttle body and air-intake cleaner, 12 ozOEMCRC 05078 / AutoZone SKU 55922
Do not spray or soak the IACV electrical coil/motor, MAF sensor or incompatible c
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Sources for this issue (2)
P0505 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0505 mean on a Honda?
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. On Honda it is documented across 1 model: Civic.
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 on a Honda?
Published repair estimates on Honda range from $50 to $300 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0505 on a different make?
View P0505 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.