YAMAHA FX500 Guitar Effects error 37

The Yamaha FX500 I own is displaying an error 37 when its turned on, although I cannot find any error list in the owner's manual to determine what's consist of error 37; At the beginning page of the owner's manual says something like this: the unit has an internal battery to keep the memory on when you turn off the device, in case the battery is out of charge the unit will show an error; and there's no mention of any number for that error, anyway I checked the 3V battery CR 2032 inside and it's fully charged; I don't know what to do for finding the meaning of error 37, please if you can help me I will appreciate. Thank you
                                                                             D. Quinones