DTC P0505: Idle Control System Malfunction (2002-2003 models)

NOTE:

Information marked with * 1 applies to K20A3 engine; * 2 applies to K20A2 engine.
If DTC P1519 is stored at the same time as DTC P0505, troubleshooting DTC P1519 first, then recheck for DTC P0505.

Start the engine. Hold the engine speed at 3,000 RPM without load (in Park or neutral) until the radiator fan comes on, then let it idle.
Check the engine speed at idle without load conditions: headlights, blower fan, rear defogger, radiator fan, and air conditioner off.
Is the engine running at 650* ¹ (700)* ² +/-50 RPM?
1. YES - Intermittent failure, system is OK at this time.
2. NO - If the idle speed is less than 600*¹ (650)*² RPM, go to step 3; if it's 700*¹ (750)*² RPM or higher, go to step 4.
Disconnect the idle air control (IAC) valve 3P connector.
Does the engine speed increase or fluctuate?
1. YES - Check the idle speed with a different load condition (electrical, A/C, gear position, P/S, etc.) (see IDLE SPEED INSPECTION ). If it's out of specification, replace the IAC valve (see THROTTLE BODY DISASSEMBLY/REASSEMBLY ).
2. NO - Replace the IAC valve (see THROTTLE BODY DISASSEMBLY/REASSEMBLY ).
Turn the ignition switch OFF.
Remove the air intake duct from the throttle body.
Start the engine, and let it idle.
Put your fingers on the lower port (A) in the throttle body.

Fig 1: Putting Fingers On Lower Port (A) In Throttle Body
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Does the engine speed drop below 700* ¹ (750)* ² RPM?
1. YES - Check the idle speed with a different load condition (electrical, A/C, gear position, P/S, etc.) (see IDLE SPEED INSPECTION ). If it's out of specification, replace the IAC valve (see THROTTLE BODY DISASSEMBLY/REASSEMBLY ).
2. NO - Check for vacuum leaks at these parts.
  - PCV valve
  - PCV hose
  - EVAP canister purge valve
  - Intake manifold
  - Throttle body
  - Brake booster hose
  - Intake air bypass control thermal valve