2000 Yaris coolant light woes - Toyota Yaris Forums

BeanBayli55 · 07-30-2022, 12:40 PM

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

sh0rtlife · 07-30-2022, 06:09 PM

isnt the blu or green one saying the engine hasnt warmed up?..or am i miss remembering?

ex-x-fire · 07-30-2022, 06:31 PM

I'd scan it for data. Look at what the computer is seeing.

BeanBayli55 · 07-31-2022, 11:15 AM

Quote:

Originally Posted by sh0rtlife

isnt the blu or green one saying the engine hasnt warmed up?..or am i miss remembering?

yes its that light.

there are no codes showing on obd.

suggested elsewhere that its likely to be the other sensor near the rear of the block as there are technically two sensors for the temperature, i changed the coolant temperature sensor, other one is identified as radiator fan switch which from what ive been told is a single wire sensor that controlsd the light so ive ordered that and will see how that goes.

Turbiini · 08-01-2022, 12:50 AM

2 or 3 pin sensor? if 3 pin 2 of them are for ecu and 1 is for meter (or light) then it might be wiring problem near sensor.

if 2 pin version then meter gets signal from ecu.

BeanBayli55 · 08-03-2022, 03:28 PM

update: ok so i changed the other sensor today, the one with the single pin and its made no difference at all.

the light stays on still almost permanent it may go off whilst driving for a minute or two then comes back on and stays on.

everything is working as it should, the ecu is reading the temperature fine, it gets up to 93 degrees , the fan will come on , temp goes down to 85 then fan turns off. both rad pipes get hot at this point so thermostat is working just fine

BeanBayli55 · 08-06-2022, 01:49 PM

i disconnected the battery for half hour this morning and during that time, pulled the dash and cleaned the connectors and on the bulb itself, gave the wires a little wiggle.

SO far its looking like its working again, it will go out now after a few minutes as it should and on a half hour drive it never came back on so fingers crossed its sorted.

thanks for all your help with this.

07-30-2022, 12:40 PM	#1
BeanBayli55 Drives: 2000 Yaris Join Date: Jul 2022 Location: Uk Posts: 4	2000 Yaris coolant light woes 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

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07-30-2022, 06:09 PM	#2
sh0rtlife Drives: 2007 5dr canadian import Join Date: Dec 2016 Location: pacific north WET Posts: 1,025	isnt the blu or green one saying the engine hasnt warmed up?..or am i miss remembering?

07-30-2022, 06:31 PM	#3
ex-x-fire Drives: 2010 yaris 3 door hatch Join Date: Jun 2013 Location: Sheboygan Falls, Wi. Posts: 506	I'd scan it for data. Look at what the computer is seeing.

08-01-2022, 12:50 AM	#5
Turbiini Drives: 1983 carina 2NZ-FTE Join Date: Dec 2020 Location: finland Posts: 34	2 or 3 pin sensor? if 3 pin 2 of them are for ecu and 1 is for meter (or light) then it might be wiring problem near sensor. if 2 pin version then meter gets signal from ecu.

08-03-2022, 03:28 PM	#6
BeanBayli55 Drives: 2000 Yaris Join Date: Jul 2022 Location: Uk Posts: 4	update: ok so i changed the other sensor today, the one with the single pin and its made no difference at all. the light stays on still almost permanent it may go off whilst driving for a minute or two then comes back on and stays on. everything is working as it should, the ecu is reading the temperature fine, it gets up to 93 degrees , the fan will come on , temp goes down to 85 then fan turns off. both rad pipes get hot at this point so thermostat is working just fine

08-06-2022, 01:49 PM	#7
BeanBayli55 Drives: 2000 Yaris Join Date: Jul 2022 Location: Uk Posts: 4	i disconnected the battery for half hour this morning and during that time, pulled the dash and cleaned the connectors and on the bulb itself, gave the wires a little wiggle. SO far its looking like its working again, it will go out now after a few minutes as it should and on a half hour drive it never came back on so fingers crossed its sorted. thanks for all your help with this.