TM 9-2320-363-20-1 Table   3-1. Troubleshooting (Cont) Malfunction Test   or   Inspection Corrective   Action ELECTRICAL    SYSTEM   (CONT) Utility    Light   Circuits   (Cont) 2. ONLY ONE UTILITY LIGHT OPERATING. Step 1. Check backup    lamp. . If   defective, replace lamp   (page 4-284). Step 2. Disconnect lead    73B    from    defective utility   tight.   Check    for   +12    VDC at lead    73B. . If   +12 VDC is   present, go   to   step    3.    If   no   voltage is present, repair    lead    73B (page    3-2). Step    3. Check    for   continuity between socket    and   ground. . If   continuity is   indicated, replace utility   light   (page   4-224). If   no continuity is   indicated, repair    ground    lead    (page    3-2). 3. UTILITY LIGHT INDICATOR LIGHT NOT OPERATING, UTILITY LIGHTS OPERATING NORMALLY. Disconnect lead    73A    from   pin    D16    of   warning light   bar.    Check    for   +12    VDC at lead    73A. . If   +12 VDC is   present, troubleshoot warning light circuit (page 3-60). If no voltage is present, repair lead 73A (page 3-2). Electric    Horn    Circuits 3-52