[spxxx]

To piggyback onto Bern's comments, it's a hardware piece without any integrated sensors. The ECU has no idea that anything has changed in regards to your radiator.

My guess is that some other issue coincidentally popped up after your CSF radiator install. My CSF radiator has dramatically improved cooling and I haven't run into any issues.

Check electrical connections (wiring plugs for the temp gauge, electric fan, etc)