Techniques for coding and decoding redundant coding for column defects cartography. Defective cell groups identified in a memory array are redundantly encoded with a different bit pattern than the bit pattern used for functional cell groups. The identified defective cell groups are repaired using redundant cell groups in the memory array. The defective cell groups are later re-identified by checking the redundant bit pattern encoded in the cell groups. If new defective cell groups are identified, the memory array is identified as failing. If no new defective cell groups are identified, the memory array is identified as passing, and the identified defective cell groups are repaired.