ecu present but no comms

hi there i have a 2002 sri vec c 2.2 and have a mother of an electrical fault on the car ,checked all fuses none have blown and checked relays changed ecu and starter relay ,still wont crank over or kick fuel pump or anythin on i have no eml on the dash but have every other light when switch ignition on ,,ordered myself an opcom reader of ebay scanned it and keep getting

U2105 - CAN-Bus No Communication with ECM (Engine Control Module)
(00) - Present

but when you go in and check its...

ecu present but no comms