What was found
(CAN) CREW REJECTED T/O DUE TO WARNING SOUND DURING T/O ROLL AROUND 80KT. THE CREW PERFORMED T/O WARNING SYS CHECK AND CONFIRMED NO SNAG THEN SECOND T/O ATTEMPT WAS MADE HOWEVER THE WARNING SOUND OCCURRED DURING THE T/O AGAIN AROUND 100KT. MAINTENANCE PERFORMED TROUBLESHOOTING AND CONFIRMED FAULT ON INPUT/OUTPUT MODULE (IOM) NR 1. NO SNAG AFTER REPLACEMENT OF IOM NR 1 AND THE ACFT RETURNED TO SERVICE.