Where is the coolant system

You would need a scanner and an inferred temp sensor to troubleshoot the system.
You need to know what the actual engine temp is, and what the temp sensor is telling the computer.
If and when the engine reaches 220 degrees, the engine temp sensor should be sending that data to the computer and it should ground the fan relay to activate it.
Unplugging the sensor and having the fan run tells you the sensor is connected, and there should have been a trouble code set at that time.
It is possible the coolant level is low, or something else preventing the temp sensor sending the correct data.

Your coolant level switch at coolant tank may be bad,click here to see.

On the 4 cylinder motor (2.3L,2.5L), the coolant temp sensor can be located
on the left side rear of the engine, below the cylinder head.

A picture of a typical Coolant Temp Sensor (aka ECT) is below:


Be sure to partially drain coolant below the level of the sensor to avoid spillage when removing the old part. Best of luck on your repair!
Greg

The problem is the coolant tempature sensor the computor.Not familiar with your model , but the sensor is useally lacated close to the thermostat..Most are a single wire. If you touch that wire to electric ground ,the fans should come on with the key in the on position.If it has 2 wires cross the termanial in the connection and they should come on.You have 2 sensors on the coolant system. 1conrols the gauge/light on the dash and the other is for the cooling fans

Most likely place for oil into coolant is oil cooler, the aluminum box that mounts between the oil filter and a flange that comes off the block.

you wasted tons of money of a throw away vehicle all you needed to do is a full tune-up w/filter change an new oxygen sensors. They determin the air/fuel mixture along with intake air temp sensor and engine coolant temp sensor not the cat

When you said you replaced everything, did that include the temperature sending unit?
The temperature sensor just operates the cooling fan or fans for the radiator.
The temperature sending unit operates the temperature gauge in the dashboard. If that thing is faulty, the gauge won't work right.
If you did change the sending unit, it could be possible that the computor is screwing it up, but in my 41 years as a mechanic I never heard of it, when a computor goes, nothing works.

Change your coolant sensor & make sure you have enough coolant in your cooling system. Your sensor is giving the wrong info to the computor & thus the irratic operation when the engine is cold. Good luck!

There a 2 coolant temp sensors. One for the guage and the other for the computor. You need to replace the one for the computor. With a faulty coolant temp sensor for the computor, it doesn't recognize a cold start to cycle. You know when the engine idles higher when you first start it up in moring then the idle drops as the motor warms up.

The larger of the two is the coolant temperature sensor. The other is the actual gauge temperature sensor. The coolant temp. sensor gives information to the cars computor & when the car reaches a predetermined temperature, the computor changes the ignition timing allowing the car to run at normal operation temperature settings. The temperature sensor gives info to the dash board gauge &/or temp. warning light. The reason you can't start on cold days is that your coolant temp. sensor is stuck in advanced mode & the timing is to far advanced . To remedy this problem change the coolant sensor. Good luck!