2000 Yaris coolant light woes

[BeanBayli55]

Hi,

My wife’s 2000 1.0 Yaris is having troubles with the coolant light on the dash.

It stays on and blue/green most of the time, occasionally goes off but comes in again within minutes.

I understand when it should go off and on etc but it just stays on most of the time. It never goes red.

Taking the engine temperature via obd it all seems absolutely fine, fan comes on when it hits 92 ish degrees , it doesn’t fluctuate at all and is constant . Top radiator hose gets nice and hot and after 80 ish degrees as does the bottom radiator hose.

I have changed the thermostat and the coolant temperature sensor but it’s made no difference at all.

What can anybody else recommend as to why the engine always thinks it’s cold even though the ecu is getting the correct temperature?

Many thanks