The current ranges and M Series ovens report a problem as four characters — 3C20, 0221, 5521 — and the structure is the useful part: the last two say which cavity and which board saw it. The legacy and European-built machines say it differently, as an E-number such as E01 or as a message in words: COMM ERR, COOL FAN, CHECKSUM, FUSES WRONG.
Which alphabet is on your display places the appliance in time before we have asked a single question. Both are here, one page per condition, and the search above finds either.