The ECU is Engine Control Unit. I would check all the wiring for bad connections. Also, you might want to reset the ECU by disconnecting the negative battery terminal and leaving it off for 15 hours, then reconnecting it. Do whatever you can before you let the STEALERSHIP rip you off! The factory servic emanuals are available FREE on Club Frontier http://www.clubfrontier.org/forums/f23/frontier-service-manuals-available-download-46290/ You should read through them first before you do anything else.
Good luck.
Good luck.