Ricoh M016 Service Manual page 159

SC 6xx (Communication and Other Error)
EEPROM communication error
An unexpected value exists in the initialization flag of the EEPROM
669
EEPROM not connected
Defective EEPROM
1. Installing the EEPROM.
2. Replacing the EEPROM.
CTL_PRREQ_N signal does not come.
The ECB does not receive a memory address command from the controller 20
seconds after paper is in the position for registration.
688
Defective controller board
Communication error
1. Turn the machine's main power off, and then on.
2. Check if the controller board is firmly connected to the ECB.
SM
Service Call Conditions
6-9 M016/M017