Ford 2003 Mustang Workshop Manual page 3466

Condition
The fog lamps are
inoperative
The individual fog lamp is
inoperative
The fog lamps are on
continuously
Pinpoint Tests
PINPOINT TEST O: THE FOG LAMPS ARE INOPERATIVE
O1 CHECK THE PARK LAMPS
Place the headlamp switch in the PARK position.
Place the multifunction switch in low beam position.
Do the park lamps illuminate?
O2 CHECK THE FOG LAMP RELAYS
Disconnect: Fog Lamp Relay.
Disconnect: Fog Lamp Interrupt Relay.
Check the fog lamp relay and fog lamp interrupt relay; refer to Wiring
Diagrams Cell 149.
Are the relays OK?
O3 CHECK THE CIRCUIT 12 (LG/BK)
Measure the voltage between fog lamp interrupt relay connector Pin 1,
Circuit 12 (LG/BK), harness side and ground.
Possible Sources
BJB Fuse 27 (20A).
CJB Fuse 38 (20A).
Circuitry.
Fog lamp relay.
Fog lamp interrupt
relay.
Headlamp switch.
Fog lamp switch.
Multifunction switch.
Fog lamp bulb.
Circuitry.
Fog lamp relay.
Circuitry.
Fog lamp switch.
Test Step
Action
GO to Pinpoint
Test O .
GO to Pinpoint
Test P .
GO to Pinpoint
Test Q .
Result / Action
to Take
Yes
Turn off the
headlamp switch.
GO to O2 .
No
GO to Pinpoint
Test L .
Yes
GO to O3 .
No
INSTALL new
relay(s). TEST
the system for
normal
operation.
Yes
GO to O4 .
No
REPAIR the
circuit. TEST the
system for
normal
operation.