What was found
SEA - ON FLIGHT 2438, RETURNED TO GATE, WHILE TAXING FOR TAKEOFF THE YAW DAMPER DISENGAGED FOLLOWED BY ROLL MISMATCH MESSAGE. CAPT'S ADI 3 DEGREES RIGHT BANK, FO'S ADI = 0. LATER DURING RIG, PITCH MISMATCH MESSAGE CAPT'S ADI =10 DEGREES PITCH, FO'S ADI = 0 DEGREES, ALSO GOT HEADING MESSAGE. MAINTENANCE REMOVED AND REPLACED NR 1 AHRS COMPUTER. OPERATIONAL TEST PASSED. AIRCRAFT RETURNED TO SERVICE.