A trouble code P0505: Idle Control System Malfunction tells you that the fuel injection computer is having a hard time keeping the engine idling at the correct RPM.
In this tutorial I'll shed some light on what this trouble code means and some of the tests you can perform to find its cause (and solution).
Contents of this tutorial:
You can find this tutorial in Spanish here: Código P0505 ¿Qué Significa? (1997-2001 2.0L Honda CR-V) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 2.0L Honda CR-V: 1997, 1998, 1999, 2000, 2001.
What Does Trouble Code P0505 Mean?
A trouble code P0505: Idle Control System Malfunction lets you know that your Honda CR-V's idle air control system is not able to maintain the correct engine idle RPM.
To be a bit more specific, your 2.0L Honda CR-V's idle speed should be around 750 ± 50 RPM once the engine has warmed up.
If the idle is below or way above this specified idle speed, the fuel injection computer will set a P0505: Idle Control System Malfunction trouble code and will light up the check engine light.
Unfortunately, this trouble code does not indicate exactly where the problem lies or what component is the one that has failed.
Common Symptoms Of A P0505 Trouble Code
You're gonna' see one or more of the following symptoms:
- The check engine light is on.
- The engine idle RPM are too high.
- The engine idle RPM are too low.
- The engine starts but stalls (if you don't keep your foot on the accelerator pedal).
What Causes A P0505 Trouble Code?
There are several things that can cause a trouble code P0505:
- Intake manifold gasket leak.
- Leaking intake manifold vacuum hose.
- Engine coolant temperature (ECT) sensor malfunction.
- Throttle position sensor malfunction.
- Base throttle plate angle (as set by the throttle plate stop screw) is incorrect or misadjusted.
- Clogged idle air ports in the throttle body.
- Idle speed is misadjusted.
- Idle air control valve stuck closed or stuck open due to carbon blockage.
- Idle air control valve malfunction.
- Fast idle thermo valve malfunction, usually caused by coolant not being able to circulate through it (automatic transmission equipped CR-V only).
Diagnosing A P0505 Trouble Code
STEP 1: My recommendation is to first check for vacuum leaks around the intake manifold gasket area.
STEP 2: Second, check the condition of all vacuum hoses. If any vacuum hoses are leaking vacuum, replace them.
STEP 3: If no vacuum leaks are found, then the next step is to make sure that the throttle stop screw is not misadjusted.
Now, if the throttle stop screw has not been touched (adjusted), then it still has the factory adjustment and there's no need to worry about it being misadjusted.
NOTE: When the throttle stop screw becomes misadjusted, it's usually the result of it being adjusted to either lower or increase engine idle RPM to mask a rough idle condition or a high idle condition.
The throttle stop screw should never be adjusted to solve any kind of engine idle speed problem.
STEP 4: Remove and bench test the idle air control valve. Yes, it can be tested to see if it's bad or not.
NOTE: The idle air control valve has a 2-wire electrical connector and is located on the intake manifold itself and not on the throttle body.
The following tutorial will help you with this test: Testing The Idle Air Control Valve (1997-2001 2.0L Honda CR-V).
STEP 5: Once the idle air control valve is removed, check its inlet air port metal mesh screen to see if it's block with carbon.
If the inlet port metal mesh screen has debris or carbon blockage, then clean it with carburetor cleaner spray.
You can find the IAC valve cleaning procedure explained in detail here: How To Clean The Idle Air Control (IAC) Valve (1997-2001 2.0L Honda CR-V).
You should also inspect the throttle plate (in the throttle body) and make sure that it's not covered with carbon deposits. If it is, clean it with carburetor cleaner spray too.
More 2.0L Honda CR-V Tutorials
You can find a complete list of tutorials here: Honda 2.0L Index Of Articles.
Here's a sample of the tutorials you'll find there:
- How To Test For A Blown Head Gasket (1997-2001 2.0L Honda CR-V).
- How To Test The Ignition Coil (1999-2001 2.0L Honda CR-V).
- How To Test The TPS (1997-2001 2.0L Honda CR-V).
- How To Test The MAP Sensor (1997-2001 2.0L Honda CR-V).
- How To Test Engine Compression (1997-2001 2.0L Honda).
If this info really saved the day, buy me a beer!