DTC B1656: EEPROM Write Error: Description
WARNING: This page is about a different car, the 2000 Cadillac Seville. However, it is still accessible from the selected car via links, so may be relevant.
Each module performs internal tests on EEPROM each time module performs a write function to a memory address in EEPROM. Module reads back data that has been written and compares it to incoming data. If data does not match after 3 consecutive write and verify attempts, module will indicate a write malfunction is current.
DTC will set when data read back after a write does not match data being written 3 consecutive times. When DTC is set, microprocessor finds another area to write information to. This new area becomes permanent area for storage of this information.
DTC will clear when microprocessor makes a successful write to EEPROM.