As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER PUSHBACK C HYD PRIM 1 EICAS MESSAGE APPEARED JUST AFTER PUSHBACK AND BOTH ENGINES STABILIZED A/C RETURNED TO THE GATE AND MTX GROUNDED A/C . MTX VERIFIED HYD PUMP WORKING. REF AMM 29-11-00. OPS CHECK GOOD. AND RETURNED A/C TO SERVICE.