Isx Cm871 gas pedal limp mode for couple seconds while driving

[Biamarckmm12]

Short story my truck is prostar 2009 it goes to limp mode for a couple secs while driving if I let go the pedal and press it againg it will accelerate but it keeps doing it some times ... we hooked up a computer to read codes it only show ecm power lost... we check all the batteries the are only 7 months old cables and everything looks good change all the grounds and it keeps doing it ... my mechanic suspects it's the ECM going bad ... I try the tap test but nothing happens ... any help please... thanks