4-14. 12-VOLT ELECTRICAL SYSTEM TROUBLESHOOTING PROCEDURES (CONT).
12. REAR SIDE MARKER LIGHT(S) DO NOT OPERATE (S/N YB6122 075 AND UP).
Tools and Special Tools
Tool Kit, General Mechanic's: Automotive
(Item 50, Appendix J)
Multimeter (Item 28, Appendix J)
Engine OFF, (TM 9-2320-364-10)
Wheels chocked, (TM 9-2320-364-10)
12 vdc cable assembly connected to
truck, (Para 2-9)
Parking brake applied, (TM 9-2320-364-10)
The following troubleshooting procedures cover the left rear side marker light, but they apply to all rear side marker
All electrical wires and components listed in this troubleshooting procedure are illustrated and located in FO-1.1.
Truck electrical system OK.
All other trailer lights operate.
REASON FOR QUESTION
Does at least one rear side or
If no rear side or rear marker
Wire 1012B faulty.
lights operate, fault is trailer
rear marker light operate?
Wire 1435 faulty.
main wire harness wire 1012B.
Rear side marker light faulty.
If at least one rear side or rear
marker light operates, fault is
from rear junction box through
rear side marker light.
Repair wire 1012B
(see schematic, Fig
FO-1.1) or replace
trailer main wire
(Para 4-30.1). Verify
repair, go to Step 4 of