Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P0505: Idle Control System Malfunction (2000-2003 models)
- If DTC P1519 is stored at the same time as DTC P0505, troubleshooting DTC P1519 first, then recheck for DTC P0505.
- Before you troubleshoot, record all freeze data and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
- Start the engine. Hold the engine speed at 3,000 RPM without load (in neutral) until the radiator fan comes on, then let it idle.
- Check the engine speed at idle without load conditions: headlights, blower fan, radiator fan, and air conditioner off.
Is the idle speed 800 +/- 50 RPM?
- YES - Intermittent failure, system is OK at this time.
- NO - If the idle speed is less than 750 RPM, go to step 3; if it is 850 RPM or higher, go to step 4.
- Disconnect the idle air control (IAC) valve 3P connector.
Dose the engine speed increase or fluctuate?
- YES - Check the idle speed with a different load condition (electrical, A/C, etc.). If it is out of specification, replace the IAC valve (see SPECIAL TOOLS ).
- NO - Replace the IAC valve (see SPECIAL TOOLS ).
- Turn the ignition switch OFF.
- Remove the intake air duct from the throttle body.
- Start the engine, and let it idle.
- Put your fingers on the upper and lower ports (A) in the throttle body.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Does the engine speed drop below 750 RPM?
- YES - Check the idle speed with a different load condition (electrical, A/C, etc.). If it is out of specification, replace the IAC valve (see SPECIAL TOOLS ).
- NO -
Check for vacuum leaks at these parts:
- PCV valve
- PCV hose
- EVAP canister purge valve
- Intake manifold
- Throttle body
- Brake booster hose
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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