P0505 – Idle speed control system

System: Engine - idle
Dashboard light: Check engine light (MIL)
Check-engine blink code: —
Applies to: 1SZ-FE (by platform)
Description: Idle speed control system
Possible causes: Trouble area: 1.Idle speed control valve dirty or faulty 2.Air leak 3.Throttle body dirty
What to check: Checking points: 1.Clean throttle body and idle valve 2.Check for air leaks 3.Check idle valve wiring
Confidence: medium (Toyota Echo 1999–2002 factory diagnostics, same XP10 platform; not confirmed on JDM 1SZ-FE)

From the factory service material. Clear the code and test-drive to confirm it returns. Search all fault codes · Common problems · Warning lights