What was found
DURING DEPARTURE IOPS FAIL FOLLOWED QUICKLY WITH ED MON FAIL ALL DATA FROM ED WENT AWAY A/C RETURNED TO FIELD W/O ANY OTHER PROBLEMS AT TOUCH DOWN WEIGHT IN WHEELS FADEC/DU DISPLAYED ON ED WITH AVIONICS CAUTION OCCURED. REMOVED FROM SERVICE. INTEROGATED CDS EDU MON FAIL FAULT DISPLAYED WITH NO OTHER FAULTS INDICATED REPLACED EDU IAW Q400 AMM 31-61-01-000-801/400-801 OPS TEST OF EDU 31-61-01-710-803 C/W IOP 1&2 TEST QX MTC6314101 CHECK GOOD C/W CDS IOPS TEST IN CDS TEST OK. RETURNED TO SERVICE.