Cold Engine Light Won't Turn Off...

[yarisitis]

My girlfriend has a 2000 Toyota Echo w/ 150,000 miles on it. Last night it was around 30 degrees and we sat in the car for a few minutes to let it warm up and then started driving to our destination thinking it would finish warming up and the light would turn off on the way like it always does. Well it didn't...

The cold engine light stayed on the entire 20 minute/15 mile drive to our destination. It was only after we got there and turned the car off, and then back on that the light finally turned off right away. It happened again tonight to my girlfriend on her way to work.

Any ideas if this is could be a bigger problem? We're in CA so it doesn't get very cold where we are, lowest it probably gets is around 15-20 degrees, but never has the cold engine light stayed on for a significant amount of time.


EDIT: Whoops! Didn't see the dedicated "cold weather" threads. Mods feel free to move this post into the other threads and delete this one.

[CTScott]

Most likely the coolant temperature sensor is failing. You can easily tell if you can find someone with a scangauge type device, which will let you display the temp that the ECM is seeing from the sensor.