Hello,

2001 ford ranger 2.3 liter. My check engine code ame on a few weeks back got P0125 / COOLANT. According to your posts, I should change my t-stat and ect sensor, correct. Have any of you changed the ect on the ford? Is it right behind the engine almost invisible? Any suggestions on how to reach /see it? Also, where is the t-stat. Which should I start with? T-stat or ect

Thanks in advance

 

PO125 = Engine coolant temp not high enough to enter closed loop operation.

This would suggest the engine is over cooling & if true, probably from a stuck open thermostat imo.

So, begin with your temp gauge, does it indicate that the engine isn't warming up???
Does the heater put out cold or barely warm air????
Is the top radiator hose barely warm, after the engine has run long enough to be fully warmed up????

If the answers are "yes" then it's likely the thermostat is acting out & stuck open, or someone has removed it. It should be in the engine side casting, that the upper radiator hose connects to.

If the temp gauge is indicating the engine is warm & the heater is putting out good heat & the top radiator hose is hot enough to be uncomfortable to touch, then it's likely the computers engine coolant temp sensor is acting up & lying to the computer about the true engine coolant temp, or maybe the sensors electrical connection is somehow corrupt.

If the heater is putting out good heat & the top radiator hose is too hot to hold, but the temp gauge says the engine is cold, then you also likely have a faulty temp gauge coolant sensor, or it's electrical connection is somehow corrupt, or the gauge is acting out, which is less likly imo.

Note that the temp gauge & computer use different temp sensors.

Just some things to check, to try & isolate the problem.
Let us know what you find.

If you don't have a repair guide, try AutoZones web site repair/parts locator, for your parts location, or stop by your local library & check out a repair guide.

Just some things to try & thoughts to ponder.

 

99% of the time this code is set by a stuck open thermostat. Basically the computer expects to see a warm engine within a certain amount of time, and if it doesn't it sets this code.

I would suppose a bad temp sensor could cause this, but it would have to be bad in a way that the circuit wasn't open, nor shorted, and be biased cold. Possible, but very improbable.

Good luck