check engine light

What was the fault code and are there any other symptoms?

He did not tell me a fault code. No other symptoms. No noise. Drives fine. New radiator and coolant is full.

If the radiator fan turns on in city driving with the AC turned off, the coolant temperature sensor is working. That is a very low failure item. A fault code related to that is more likely to be the result of a loose electrical connector, or it was unplugged while the ignition switch was turned on. The Check Engine light will turn off when the connection problem is taken care of but you might have to restart the engine.

If the thermostat is sticking open, the fault code will be "engine is cold too long". You should also notice that on the temperature gauge, and the air from the heater will no longer burn your hand if you hold it close to the floor duct.

Then I'll bet it is the thermostat. I did notice the temp gauge showed cooler than what it should have been. After about 8 more miles of driving, it went up to the normal range on the gauge.