As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA FLIGHT NR 2262 - ATC ADVISED THEY HAD NO TRANSPONDER ON RADAR. TRANSPONDER TRIED IS ON, NR 1 AND NR 2 POSITION, REPLY LIGHT NORMAL. MAINTENANCE REPLACED ATC CONTROL HEAD UNIT. PERFORMED ATCBS/MODE-S TRANSPONDER TEST IAW TASK CARD 9345001. OPERATION CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.