Possible cause

Connector terminal disconnection, poor contact, damage, deformation, corrosion
Position memory control module power supply voltage or body ground malfunction
Open circuit in wiring harness between position memory control module and connector C-55
Open circuit in wiring harness between connector C-55 and connectors C-51, C-52
Connector C-55 malfunction
Connectors C-51, C-52 malfunction
Position memory control module malfunction