Hard start, poor fuel mileage,...
Low coolant or bad sensor
What type of coolant sensor? The below answer is for the coolant LEVEL sensor. The coolant TEMPERATURE sensor on my vehicle is located just next to the thermostat housing. On the front top center area of the engine just behind the radiator. Follow the coolant hoses if you have trouble. On my 1995 Jeep Grand Cherokee the sensor is located on the top of the plastic coolant reservoir tank. Look for a small (2-wire?) electrical connector.
It is the two wire sensor next to the thermostat housing.
On the coolant overflow bottle that in on the passenger side of the engine.
sensor is in the plastic reserve on the float.
IN THE WATER JACKET.
The engine computer uses the signal from the coolant temperature sensor to decide when to activate the radiator fan relay.
Don't worry about it those screens are all faulty & blink coolant temp sensor.
The coolant temperature sensor on a 2001 Jeep Cherokee is located in the intake manifold. It monitors the flow and temperature of coolant through the engine.
There are two separate sensors that play here. the "coolant temperature sensor" and "coolant LEVEL sensor". I suggest confirming which of these was replaced, as it is very common for them to be confused. likely you will find the coolant sensor that was replaced was the one on the engine (temperature); The LEVEL sensor is mounted either in the coolant resivoir or in the radiator. Probably just need the proper sensor replaced.
if it is a 96 like mine it is on the top of the coolant resovoir. it is rounnd and has an electrical connector attached to it
The computer is not seeing a voltage drop across the coolant sensor. You could have a bad sensor, broken wiring, or a bad computer.