Trouble Code: Honda P0505 – Idle Air Control Valve

Likely Cause:

  • Faulty IACV-AAC valve
  • IACV-AAC valve harness is open or shorted
  • IACV-AAC valve circuit poor electrical connection

The problem is very common with Honda Civic and Honda Accord vehicles, and adjusting the engine idle speed usually takes care of the problem, also there is a service bulletin for the following Honda models:

What does the Honda P0505 code mean?
The Honda P0505 code is set when the IACV-AAC valve does not operate properly.


  •  Engine Light ON (or Service Engine Soon Warning Light)
  •  Engine hard to start
  •  Rough or erratic idle speed

Honda P0505 DTC Description:
This system automatically controls engine idle speed to a specified level. Idle speed is controlled through fine adjustment of the amount of air which by-passes the throttle valve via Idle Air Control Valve IACV) and Auxiliary Air Control AAC) Valve. The IACV-AAC valve changes the opening of the air by-pass passage to control the amount of auxiliary air. This valve is actuated by a step motor built into the valve, which moves the valve in the axial direction in steps corresponding to the Engine Control Module (ECM) output signals.

One step of IACV-AAC valve movement causes the respective opening of the air by-pass passage. (i.e. when the step advances, the opening is enlarged.) The opening of the valve is varied to allow for optimum control of the engine idling speed. The crankshaft position sensor (POS) detects the actual engine speed and sends a signal to the ECM. The ECM then controls the step position of the IACV-AAC valve so that engine speed coincides with the target value memorized in ECM. The target engine speed is the lowest speed at which the engine can operate steadily. The optimum value stored in the ECM is determined by takig into consideration various engine conditions, such as during warm up, deceleration, and engine load (air conditioner, power steering and cooling fan operation).

Applicable For:
2012 Honda S Concept
2012 Honda Ridgeline Sport
2012 Honda Pilot
2012 Honda Odyssey
2012 Honda NSX Concept
2012 Honda Insight
2012 Honda Fit Sport
2012 Honda Crosstour
2012 Honda Civic Si Sedan
2012 Honda Civic Si Coupe
2012 Honda Civic Hybrid
2012 Honda Civic HF
2012 Honda Civic EU-Version
2012 Honda Civic Coupe
2012 Honda Civic
2012 Honda C Concept
2012 Honda CR-Z
2012 Honda CR-V
2012 Honda Accord Coupe Concept
2011 Honda Odyssey
2011 Honda Jazz Hybrid
2011 Honda Jazz
2011 Honda EV-Ster Concept
2011 Honda Civic Type R Mugen 2.2
2011 Honda Civic Si Concept
2011 Honda Civic Concept
2011 Honda CR-Z Mugen RR Concept
2011 Honda CR-Z Mugen Concept
2011 Honda CR-Z
2011 Honda CR-V Concept
2011 Honda Accord Type S
2011 Honda Accord Tourer
2011 Honda Accord EU Version
2011 Honda Accord Coupe
2011 Honda Accord
2011 Honda AC-X Concept
2010 Honda Odyssey Concept
2010 Honda New Small Concept
2010 Honda Insight EU Version
2010 Honda Insight
2010 Honda HSV-010 GT
2010 Honda Fit EV Concept
2010 Honda FCX Clarity
2010 Honda CR-V US-Version
2010 Honda CR-V
2010 Honda Brio Concept
2010 Honda Accord Crosstour
2010 Honda 3R-C Concept
2009 Honda Skydeck Concept
2009 Honda Ridgeline
2009 Honda Pilot Prototype
2009 Honda Pilot
2009 Honda P-NUT Concept
2009 Honda Odyssey
2009 Honda Legend
2009 Honda Jazz
2009 Honda Fit
2009 Honda FCX Clarity
2009 Honda Civic Hybrid
2009 Honda City
2009 Honda CR-Z Concept
2009 Honda Accord Tourer
2009 Honda Accord
2008 Honda S2000 Type S
2008 Honda S2000 CR
2008 Honda S2000
2008 Honda Odyssey
2008 Honda OSM Concept
2008 Honda Insight Concept
2008 Honda Fit
2008 Honda FC Sport Concept
2008 Honda Accord
2007 Honda Fit
2007 Honda Element SC
2007 Honda Civic
2007 Honda CR-V
2007 Honda Accord
2006 Honda Legend
2006 Honda FCX Concept
2006 Honda Element
2006 Honda Civic
2005 Honda Civic
2004 Honda S2000
2004 Honda Odyssey
2003 Honda Pilot
2003 Honda Element
2003 Honda CR-V
2003 Honda Accord Sedan

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