Is it required to get the ECM update when you get the thermostat/gasket replaced?

Question

My 2006 hyundai accent was overheating per the indicator as well as the check engine light. I took it to get repaired. I got the thermostat and gasket replaced and coolant added. They recommended, not required, I do an ECM update, I choose not to. However, when I picked the car up they warned me the check engine light was still on because I didn't do the ECM. I drove a ways the RPMs were irratic, the overdrive light is flashing and hear a loud thump when shifting from park to drive. Do you think this is to do with the ECM? I did not have any problems like this until I brought it into get the original work done.

Answer 1

I mean if the ECU update is for that problem, you have to get it updated. what is the update for? usually its to fix an issue