2001 Ford Explorer Sport Trac - CEL question

My car the check engine is light on. What is the main problem ? My mechanic he take out the thermostat because he said in the hot countries is not necessary. Please give me an advise . Thank u

Your mechanic is wrong taking the thermostat out . Where are you located because without knowing the code it is impossible to know why your check engine light is on . Why did he not tell you what the code was ? If you are in the US most Auto Zone stores will read the codes . Post the actual codes here .

With a nineteen year old vehicle there is a plethora of possible problems leading to the CEL coming on.
Have your mechanic read the codes and report the codes here.
Could be something simple and cheap like a faulty gas cap to something expensive. Could even be related to removing the thermostat.
Have a new thermostat installed.

A correctly working thermostat doesn’t care what country it’s in or what the local climate is. You need a thermostat so the engine will run properly. If possible, find another mechanic and have the thermostat replaced. He should be able to read the codes and figure out what the problem is.

The OP’s reference to “hot countries” suggests he/she is not in the US, though that could be the result of English as a second language.