As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI OUT CENTER HYDRAULIC QUANTITY DROPPED TO ZERO. AICRAFT BACK TO BLOCK AND GROUNDED BY MAINTENANCE. MAINTENANCE REMOVED & REPLACED ACMP PRESSURE/CASE DRAIN FILTER MODULE DUE TO LEAKAGE IAW AMM 29-11-18. LEAK CHECK GOOD. NO LEAKS. AIRCRAFT RETURNED TO SERVICE.