Your problem is most likely the ECT/CTS in other coolant temp sensor located by where you replaced your thermostat. You pull the connector of the CTS and run the car and the fan should stay on. The check engine light will come on because the ECU does not recieve any signals from the CTS. But if this corrects your problem then replace the CTS. I believe the thermostat should fully open at 198 F so feel both hoses to make sure they are both hot meaning you have good circulation. Hope this helps.