Yokogawa CS3000 DCS with Redundant ALR121 communicating with redundant Allen Bradly PLC with Flex I/Os. Problem in Duplex ALR121 card, it is showing Red colour in System Status with 1C error. Master card of both DCS and PLC is healthy and communicating. Problem in redundant card only. If IOM load is given, ALR121 becomes healthy for few seconds and again fails with 1C message in system status.