3553 Train door did not open (NOC). ~~~~~ 3553 Train door did not open (NOC).  553/554 ER D/L - Done. From SIG L log, #3554 B/S unable to open doors. As preventive measure, replaced #3554 DORB 2-1. Function test - OK. (Refer to SIG L N/O 2220121)  Goh AT 44151