TM 55-1510-222-10 Table 3-4.  Malfunction Indications and Procedures Mode of Malfunction Operation Indication Procedure Probable Cause STBY or ALIGN WARN  on,  CDU  blank(DIM control     clockwise.          MSU BAT off 1. Rotate MSU mode selector OFF. Automatic shutdown caused by overtemperature.- 2.      Check   aircraft   cooling system and correct if faulty. 3.  Realign INS. STBY, ALIGN, NAV WARN   on,   MSU   BAT   on, CDU blank. 1. Rotate MSU mode selector OFF. Loss  of  INS  power  and  low battery. 2.    Insure  all  switches  and circuit    breakers    applicable to    INS    operation    are    set properly. Unit (BU). 3.    If  in  flight,  rotate  MSU mode selector OFF. 4.      If   on   ground,   replace battery   unit.      Battery   unit test   may   be   bypassed   by rotating    mode    selector    to OFF,     then     to     NAV     and reloading position coordinates.          When     INS advances to alignment State 7 (PI = 7) rotate mode selector to ALIGN. STBY, ALIGN, or NAV WARN on, CDU is operating Perform    Malfunction    Code Check as described in Table 3-3. Navigation failure or interfacing system problem. Table 3-5.  Action Codes and Recommended Actions Code Recommended Action 01 Shut down INS. 02 Watch for degradation (NAV).  During ground operation, downmode to STBY and restart alignment. 03 INS may be used for navigation.  One or more analog outputs are not functioning properly.  Check 26 VAC circuit breakers, HSI and autopilot. 04 Downmode to STBY and restart alignment (ground operation only). 05 Correct problem in interfacing system (could be INS).  Will not seriously affect performance. 3-66