As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING TAXI TO POSITION THE THE MAIN HYDRAULIC SYSTEM WAS CYCLING EVERY 30 SECONDS. THE CREW RETURNED TO COMPANY RAMP. THE IB BRAKE PRESSURE REDUCING VALVE WAS REPLACED AND THE AIRCRAFT WAS RETURNED TO SERVICE. (TC NR 20061003001)