All mine will display are E codes. How do I switch to P codes?I can tell you the OBD parameter so you can monitor the temperature.
Enter diagnostics (Off + Warmer), when you get to the 7.0 screen press Lo.
The FDC will show P.0.1. Navigate with the Hi button to P.0.4 - that is your coolant temperature displayed in Celsius. Under normal operation the thermostat shouldn't let it go much past 100C before it drops to about 80.
Check it out. Most likely your thermostat is stuck closed.