TM 9-2320-363-20-1 Table    3-1. Troubleshooting (Cont) Malfunction Test    or   Inspection Corrective    Action ELECTRICAL    SYSTEM (CONT) Backup    Light   Circuits (Cont) Step 3. Disconnect lead    420JD from   backup light   15A    fuse. Check for   +12 VDC at lead 420JD. . If   +12 VDC is   present, go   to   step    4.    If   no   voltage   is   present, repair    lead   420JD (page 3-2). Step    4. Disconnect lead    120    from   backup    light   switch. Check for   +12    VDC at lead 120. . If   +12 VDC    is   present, go   to   step    5.   If   no   voltage is   present, repair    lead    120    (page 3-2). Step 5. Disconnect lead 120B    from   backup light   switch. Press    backup light   switch. Check for   continuity between switch    contacts. . If   continuity    is   indicated, go   to   step    6.    If   no   continuity    is indicated, replace backup light   switch    (page 4-313). Step 6. Disconnect lead 120B    from chassis harness. Check for   +12 VDC at lead 120B. . If   +12 VDC is   present, go   to   step    7.    If   no   voltage is   present, repair    lead    120B    between chassis and    backup light   switch (page    3-2). Step 7. Check for   +12 VDC at backup receptacle socket 120B connector. . If   +12    VDC is   present, repair receptacle socket    ground    leads   to ground    (page    3-2). If   no   voltage is   present, repair    lead 120B    to chassis wiring   harness (page 3-2). 2. RIGHT OR LEFT BACKUP LIGHT NOT OPERATING. Step 1. Check backup light   lamp. . If   defective, replace lamp    (page 4-284). Step 2. Check for   continuity between socket and   ground. . If   continuity    is   indicated, replace backup    light   (page 4-284). If no   continuity    is   indicated, repair ground    lead    (page    3-2). Step    3. Disconnect red   lead    from   backup    light.    Check for   +12 VDC at   red    lead    (for light   on   right   side   only). . If   no   voltage    is   present, repair red   lead    (page 3-2). 3-50