Hyundai Repair: 01 santa fe, coolant temperature sensor, faulty engine

Question
My check engine was coded and came back with p0118 could u let me know what that is.

Answer
P0118 indicates an irregular coolant temperature.  This could be caused by any of the following:

-- Engine overheating (in which case you'll need to find the cause)
-- Thermostat stuck open
-- Defective coolant temperature sensor
-- Wiring issue
-- Faulty engine control module.

I've never seen a case where the wiring or the engine control module was the issue.  If you can retrieve what is called freeze frame data, it will give you the coolant temperature (as well as a few other data points) at the time the diagnostic trouble code (DTC) was set.  So, for example, if the coolant temperature is outside the range of possible temperatures, it's nearly certain that the issue is with the sensor itself.  Whereas, if the temperature at the time of the issue was within the range of believable values, you'll need to audit the cooling systems performance.