Hello,
You may have a bad thermostat that is failing to close. The open loop is basically the vehicle preventing itself from overheating when there is an issue with the cooling system.
Replace thermostat, and erase the trouble code.
If the code returns, or the fans still activate before normal operating temperature, let me know.
RepairPal Certified shops can diagnose and repair your 2001 Chevrolet Prizm. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.