That error code means Fuser Overheat Error 1, Hot Roller Fusing Lamp Overheat. This has happened due to faulty or dirty/worn out heating roller thermistor. Try turning off the copier for 1-2 hours and let it cool down. Now check if error disappears. If error is still there you'll need to clean/replace the thermistors.
The thermistor is located with the fuser unit inside the machine.
A replacement thermistor can be bought from here: http://www.precisionroller.com/thermal-control-devices-for-ricoh-4420l/details_27143.html