What was found
FLT BOS-IAD DIVERTED TO DCA, CLIMBING THROUGH 15,000FT "PARKING BRAKE NOT RELEASED" EICAS MESSAGE APPEARED. ATTEMPTED BRAKE RE-CYCLE MESSAGE WENT AWAY ON ROLL-OUT, WHICH WAS NORMAL. AFTER LANDING EMERGENCY BRAKE FAULT EICAS MESSAGE ILLUMINATED. FOUND EMERGENCY BRAKE PRESSURE SWITCH NR 1 INDICATING PRESSURE IN SYSTEM. REMOVED AND REPLACED EMERGENCY PARKING BRAKE SWITCH NR 1 PER AMM 32-44-09-000-801-A. REMOVED AND REPLACED EMERGENCY PARKING BRAKE VALVE PER AMM 32-44-01-000-801. OPS CHECK NORMAL.