'01 3.0 165,00mi
im driving to town, 15mi from home. half way there I notice the temp gauge hadn't moved much. thats odd, wonder whats up. on the way home it got up to where its normal. so its kinda been like this for a week or so. the other day im just moving the truck out of the carport and I see the CEL is on. humm. later I pulled out the OBD2 reader and got the code P0125. Insufficient Coolant Temperature For Closed Loop Fuel Control. makes sense, so im thinking the sender is good? it moves from cold to normal must be the thermostat. its not too old, like 7mo. I got it at Napa 195 temp. I guess I'll check the temp sensor, but im still thinking thermostat.

any ideas?

 

P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control

There are two temp reading devices on 2001 3.0l
The ECT sensor, 5volt, only used by the computer
The Temp Sender, 12volt, only used by the dash temp gauge

If BOTH were showing low temp, slow warm up, then it was/is most likely a thermostat issue
Temp gauge should show warm up within 2 or 3 minutes, and then full warm up, gauge just below 1/2 after 5 to 8min of drive time
Also feel Heater temp, set temp to HOT and turn fan on, thats the actual coolant temp at that time, to confirm dash temp gauge reading

The Computer is what sets the P0125 code so the ECT sensor initiated that code, but if dash temp gauge also showed slow warm up then its not a sensor or sender issue, coolant is actually too cold, so thermostat issue

Thermostats are suppose to "fail open" when they fail, its called "fail safe", to prevent overheating, not always how it happens, lol, but in this case its a good way to fail

 

im going to town today, I'll do the heater check. most likely get aThermostat. I need a thermostat housing too. the one I have is pretty used up. im surprised it isnt leaking.

 

driving to town today the temp gauge didnt move much but it did move and the heater wasn't too hot, Kina warm.

 

Thermostat is bad