Where would you find the engine coolant temp sensor on a 1989 Jeep Cherokee?

Low coolant would be because the coolant is low or the sensor has failed, Check engine light would be because the computer has detected a problem and set a code.

Make sure you have engine coolant. If the engine isn't getting enough coolant, it will overheat, stall and possibly destroy the engine. One symptom is that no coolant is circulated into the heater. Also check the crank sensor, but check coolant first...then the crank sensor.

A coolant sensor could be a liquid level sensor and the other is a temp sensor OR The coolant is different temperatures at different places inside the engine and way way cooler when it comes out of the radiator so where the two sensors are mounted can cause difference's. OR they are two different pieces and calibration will not be identical and they will produce slightly different readings.

(based on a 96 civic LX) I believe the engine coolant temperature sensor is located on the side of the engine (opposite of the camshaft). If you need more details, I would recommend you to download the service manual on www.manualnguide.com

That would be the engine coolant temp sensor for the dash gauge only. The sensor near the thermostat housing is the engine temp sensor for the ECM.