DTC P0505: Idle Control System Malfunction

NOTE:

If DTC P1519 is stored at same time as DTC P0505, troubleshooting DTC P1519 first, then recheck for DTC P0505.

Start the engine. Hold the engine at 3,000 RPM with no load (in Park or neutral) until the radiator fan comes on, then let it idle.
Check the engine speed at idle with no-load conditions: headlights, blower fan, rear defogger, radiator fan, and air conditioner are not operating.
Is the engine running at 720 50 RPM?
1. YES - Intermittent failure, system is OK at this time.
2. NO - If the idle speed is less than 670 RPM, go to step 3 if it's 770 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 (see IDLE SPEED INSPECTION ).
2. NO - Replace the IAC valve.
Turn the ignition switch OFF.
Remove the air cleaner from the throttle body (see AIR CLEANER REPLACEMENT ).
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 In Throttle Body

Does the engine speed drop below 770 RPM?
1. YES - Check the idle speed (see IDLE SPEED INSPECTION ). If it's out of specification, replace the IAC valve.
2. NO - Check for vacuum leaks. Make sure the throttle valve is completely closed, and repair as necessary.