As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE IN DESCENT AT 250KTS, UNABLE TO TRIM THE AIRCRAFT WITH THE RUDDER TRIM. TURNED OFF A/P AND YAW DAMPER, STILL NO GOOD. TURNED OFF BLUE SYSTEM HYDRAULICS AND IT WORKED. REMOVED AND REPLACED RUDDER PCU IAW MM 27-22-01. OPS CHECKS AND LEAK CHECKS GOOD.