What was found
IN PREPARATION FOR APPROACH INTO KBUR, WHEN AUTOBRAKES WERE SELECTED IN LOW OR MED THE AUTOBRAKE FAULT LIGHT ILLUMINATED (PREVIOUS WRITE UP). CONTACTED GOCC AND DIVERTED TO KLAX FOR MAINTENANCE. FOUND GROUND AT PIN B AT THE VALVES. REMOVED AND REPLACED 89GG MASTER VALVE. CHECKED FILTER AT MASTER VALVE MANIFOLD FOUND NO DEFECTS. PERFORMED NORMAL BRAKING SYS, OPS CHECK NORMAL MM32-42-25, IPC 32-42-03, AWM 32-42-07 AND ASM 32-42-07.