As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER PUSH BACK & PRIOR TO TAXI C HYD PRIM ONE ILLUMINATED. AIRCRAFT BACK TO BLOCK AND GROUNDED BY MAINTENANCE. MAINTENANCE SWAPPED C1 & C2 ELCU IAW AMM 29-11-14 C1 PUMP OPS CHK GOOD. C2 HYDRAULIC PUMP DEFERRED IAW MEL 29-11-2. PLACARD INSTALLED. AIRCRAFT RETURNED TO SERVICE.