P0133 – Front oxygen sensor slow response

System: Engine - O2
Dashboard light: Check engine light (MIL)
Check-engine blink code: —
Applies to: 1SZ-FE (by platform)
Description: Front oxygen sensor slow response
Possible causes: Trouble area: 1.Front oxygen sensor 2.Exhaust leak before the sensor
What to check: Checking points: 1.Check for exhaust leaks 2.Replace sensor if slow
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