Dash8 First Officer reports five engine ECU (electronic control unit) failures over a period of three days; with an equal number of attempted repairs and MEL's.

Narrative

At the end of the runway the #2 engine man caution light illuminated. The Captain contacted Maintenance and the #2 ECU was MEL'd. It had been MEL'd the day before and was cleared by resetting circuit breakers. Once we got to LGA; the MEL was cleared and we were late for our next flight. We taxied out to the runway and the #2 engine man caution light illuminated again. The Captain again contacted Maintenance and the #2 was MEL'd again. On takeoff; I was pilot flying and at 100 feet the #1 engine man caution light illuminated. We contacted Maintenance Control and Contract Maintenance was sent out along with a company maintenance technician. We originated the same airplane the next day. The #2 ECU was replaced and circuit breakers were reset on the #1 side. We taxied out and departed and the #1 engine man caution light illuminated at 100 feet. Once we got to destination the Captain called and the #1 ECU was MEL'd again. Maintenance came out and after an hour the beta backup system was MEL'd. We completed a runup and we were able to sign off the aircraft. In total we had four ECU failures in three legs; and there was a total of five ECU failures in 3 days. The ECU continually failed and maintenance made repeat sign offs. The circuit breakers were reset twice on the #2 side and it kept failing and were reset once on the #1 side; only to fail. Have maintenance complete work on an MEL'd item instead of repeatedly resetting circuit breakers.