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My car temperature suddenly drops down while driving and won't move until I remove the battery and put it back... What could be the cause pls?
I have change the engine coolant temperature sensor or do I need to change again? And I was told it is not the thermostat ....
Could it be wiring?
You should scan the engine for codes. On a Saturn you can have a P0128 (low coolant temp) code for a while with no check engine light. When you get a P0128 code, the ECM will turn on the engine fans, disable the air conditioning and send the temperature gauge on the instrument panel all the way to cold. (It does these things to save the engine in case the coolant temperature sensor is giving a false low reading and the engine is actually overheating.) In this case it will reset if you disconnect the battery.
Since you will be reading codes, also check the engine coolant temperature with the scan tool. If the engine should be warmed up by driving normally but the temperature is lower than 190-200F (88-93C) then this is certainly a bad thermostat or a bad or leaky thermostat gasket or O-ring.
Even if someone told you the thermostat is good or if it is relatively new, a bad thermostat is the most common cause of the temperature gauge dropping to zero after climbing for a time on a Saturn and some other GM cars.
