What was found
APU CSS ATTEMPT TEMP EXCEEDED 980F, SHUTDOWN AND FAULT LIGHT ILLUMINATED. ACFT GROUNDED. ACCOMPLISHED APU BITE CHECK, FOUND FAULT CODE 49-31016 OVERTEMP SHUT DOWN ON CURRENT STATUS. CHECKED OTHER OCCURENCES AND FOUND CODE 49-31016 LOGGED ON 1, 10, AND 11. FAULT DOES RESET AFTER NORMAL SHUTDOWN. TSR ISSUED, REF MM 49-41-6. REPLACED START CONVERTER UNIT. OPS NORMAL, REF SAME MM W/1 APU START, SHUTDOWN. COMPLETED APU OPS TEST IAW AMM 49-11-00-710-801. OPS CK NORMAL.