P0116 – Coolant temperature sensor range / performance

System: Engine - ECT
Dashboard light: High coolant temperature light · Check engine light (MIL) · Low coolant temperature light (blue)
Check-engine blink code: —
Applies to: 1SZ-FE (by platform)
Description: Coolant temperature sensor range / performance
Possible causes: Trouble area: 1.Coolant temperature sensor 2.Thermostat stuck open 3.Cooling system
What to check: Checking points: 1.Check coolant level 2.Check thermostat opens at the right temperature 3.Check sensor reading against a thermometer
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