I have a 2000 F-150 5.4L. Got a code Po125 today. Eng. service light is on.
Autozone says it means the pcm has determined that the amount of time it took for the coolant temperture sensor to reach an input value consistent with closed loop operation was to excessive. Can anyone tell me what to check for?

 

It means the engine isn't warming up fast enough. Either the thermostat isn't closing completely or the temp sensor is bad.

 

Where is the temp. sensor on a 5.4? I could not find it.

 

There is one sensor on the drivers side head in front of the #5 intake port. I'm not sure if this one measures coolant temp or the head temp for the gauge.

 

I cleared the code without doing anything. So far it hasn't came back.

 

Perhaps the thermostat stuck open one time. Might not be a bad idea to change it just to be sure it doesn't stick again if it did. Sticking closed would be worse that sticking open.

 

Time for a new thermostat. Replace it now before it causes further problems of a more serious nature.

Steve

 

I plan on flushing the cooling sys. soon anyway. I will change the thermostat at the same time. Thanks