2004 545i with N62 engine.

I got a CEL a while back for coolant temperature too low. I don't remember the actual code number.

I replaced the thermostat, but the fault came back.

This past weekend I replaced the temp sensor in the big hose at the radiator. I haven't driven it enough yet to know if that solved the problem.

Any ideas what else could be the problem (in case the fault comes back)?

Thx.