MIS300

I have a problem with my 01 IS300 (auto). My coolant temp gauge has not been working but it's not the coolant temp sensor on the right side of the block, under injector #1. I went through the process of boiling my sensor while measuring resistance and it checks out fine.

Ive searched feverishly the last week to no avail. I heard with other lexus models that theres a separate sensor that feeds the gauge only in addition to the one that feeds the ECU.

Does the IS300 have one of these sensors, and where? Or does the sensor under injector #1 feed both the ECU and the gauge? Does the ECU feed the gauge? How does this system work? Whats the meaning of life?

Any help you guys can give would be greatly appreciated!

MIS300

I'm guessing the sensor that feeds the ECU that tells it it's cold is also the sensor that somehow feeds the guage because, upon start up when it's cold, it idles at 700-900 as if it's already warm.

Anyone have any experience with this?

MasterKwan

You can use an OBD2 scanner to see what temp the engine thinks it is. That's what I'd do anyway.

The ECU tells the gauge what to display. The gauge isn't directly connected to the sensor.

MIS300

Thanks for your input!

I will check the temp reading with the scanner. It's possible that the gauge is dead but that's just an odd problem to have. Have you heard of this happening?

MIS300

Problem solved!

Turns out the plastic connector for this sensor is unusually brittle and the inside started to break up, restricting the plug from fully engaging the sensor. I cleaned it up, removed all the loose chunks and used a long screwdriver to positively seat the connector on the coolant temp sensor. All is better. And good thing too because when the engine is cold, it didn't like to start because the computer was thinking it was warm. No more CEL, no more flashing TRAC light. Runs like a top.