coolant temperature sensor
 

My 2001 s type ,4.0 with 56,000 miles has the engine management light glowing. Auto Zone checked the codes and told me it was PO125.I checked the coolant level and it is OK.The car runs perfect.I noticed the engine management light when I drove away from a car wash.What are the symptoms of a bad temp coolant sensor?
Thanks

More likely its the thermostat stuck open.

coolant temperature sensor
 

Went for a drive this morning and car reached normal operating temp(middle of gauge) in about one and 1/2 mile of driving.Engine runs perfect.Must be the coolant temp sensor. I think I will wait a few days and see if it resets itself.I assume replacing the sensor is not a difficult job.
I will appreciate any other comments.

It's using that sensor to decide the gauge reading so you're no further forward.

If it happened right after a car wash water probably got in sensor connector. I would suggest removing the just the electrical connector and spraying some contact cleaner on the contacts to displace any remaining moisture.

Actually it's probably nothing. One of two things happened in that car wash. Either the water caused the engine to take too long to warm up to operating temp, if the car had just been started; or if it was at operating temp, the water cooled it down in a manner that the ECM knows shouldn't happen. It knows it should rise to temp at a certain rate, and that once there it should pretty much stay there. P0125 tells you it didn't stay there, in this case the car wash is the culprit.

Cheers,

I was having a temp gauge issue…the needle would go to hot, but the car was not overheating….i changed the coolant temp sensor but that wasn't the problem…it turned out the coolant reservoir had a pin hole leak, and it must suck air in and then cause a false reading….changed that and never had a another problem….some guys also refer to it as the digas bottle.