A 2002 Ford Explorer would have come from the factory with
approximately a ( 192 * Fahrenheit engine cooling thermostat )
Trouble code P0128 means:Coolant thermostat (coolant temp below thermostat regulating temp)
197 degrees Fahrenheit , according to fordparts.com
Trouble code P0128 means:Coolant thermostat (coolant temp below thermostat regulating temp)
Your thermostat might be stuck open
According to one of Fords websites : A 1995 Ford Explorer , 4.0 liter EFI , V6 engine takes : ( the Motorcraft RT-1086 engine cooling thermostat , 197 * Fahrenheit )
Low on coolant, sticky thermostat, loose connections, faulty sending unit.
Bad ground somewhere
The engine temp gauge is in the instrument cluster and the sending unit for the temperature gauge is in the intake manifold just to the left of the thermostat housing when you are looking from the front of the Explorer ( the larger sending unit to the right of the thermostat housing is for the EEC IV system)
mounted right above the thermostat where the uper radiator hose meets the engine
Trouble code P0128 means:Coolant thermostat (coolant temp below thermostat regulating temp)
that is probably an oil pressure switch that you see. coolant temp sensor is usually near the thermostat in the manifold.
To change the coolant temperature sensor on a 2002 Ford Explorer Sport Trac 4.0, first, ensure the engine is cool and disconnect the negative battery cable. Locate the coolant temperature sensor on the engine, usually near the thermostat housing. Disconnect the electrical connector and remove the sensor using a wrench. Install the new sensor, reconnect the electrical connector, and reattach the battery cable.