My 2001 F-150 4.6 is throwing code P0117 Insuficient coolant temp. My truck runs great ,it's not overheating at all. gauge is normal, the only thing I noticed is alot lower gas milage since throwing the code. I replace the thermostat & cleared the computer, but the light come back on the next morning. My truck doens't have a coolant temp sensor usually located next to the alternator, there just a threaded plug there. Do I have a CHT sensor or ECT sensor? And if so where are they located???

 

You said the code is insufficient coolant temp so it shouldn't even be close to overheating. The reason for the worse gas mileage is because it is using more fuel to try to get the motor to normal operating temperature. You already did the fix I was going to mention. I'm not sure what else it could be. Here are a few things that come to mind.

Bad temp sensor
Bad wiring between sensor and PCM
Something went **** up in the PCM

 

You have a CHT sensor....under the intake manifold on the drivers side towards the front....

 

Here is a reference from the Ford PCED manual. first Look at you're connections and possible wiring harness damage, then I would try a new sensor. ³ P0117 - Engine Coolant ³ Indicates the sensor ³ ù Grounded circuit in ³ ECT V PID reading less ³
³ Temperature (ECT) ³ signal is less than ³ harness ³ than 0.2 volts with ³
³ Circuit Low Input ³ Self-Test minimum. The ³ ù Damaged sensor ³ key ON and engine OFF ³
³ ³ ECT sensor minimum is ³ ù Improper harness ³ or during any engine ³
³ ³ 0.2 volts or 121øC ³ connection ³ operating mode ³
³ ³ (250øF). Note on some ³ ù Damaged PCM ³ indicates a hard ³
³ ³ vehicles that are not ³ ³ fault. ³
³ ³ equipped with an ECT ³ ³ ³
³ ³ sensor, CHT can be ³ ³ ³
³ ³ used and can set this ³ ³ ³
³ ³ DTC. sorry for the way it comes out but Ford protects their information.

 

Holy smokes guy, I think you need an interpreter!

Description:

Indicates the sensor signal is less than Self-Test minimum. The ECT sensor minimum is 0.2 volts or 121°C (250°F). Note on some vehicles that are not equipped with an ECT sensor, CHT can be used and can set this DTC

Possible Causes:

Grounded circuit in harness
Damaged sensor
Improper harness connection
Damaged PCM

Diagnostic Aides:

ECT V PID reading less than 0.2 volts with key ON and engine OFF or during any engine operating mode indicates a hard fault

 

I've had fan clutches lock up and run continuously before, allowing the engine to run a hair too cool causing this code.