Ford 2003 Mustang Workshop Manual page 3469

Is the resistance less than 5 ohms?
PINPOINT TEST Q: THE FOG LAMPS ARE ON CONTINUOUSLY
Test Step
Q1 CHECK THE FOG LAMP RELAY
Disconnect: Fog Lamp Relay.
Are the fog lamps off?
Q2 CHECK FOG LAMP RELAY
Check the fog lamp relay; refer to
Wiring Diagrams Cell 149.
Is the fog lamp relay OK?
Q3 CHECK FOG LAMP SWITCH
Disconnect: Fog Lamp Switch C240.
Are the fog lamps off?
Result / Action to Take
Yes
GO to Q2 .
No
REPAIR Circuit 478 (TN/OG). TEST the system
for normal operation.
Yes
RECONNECT the fog lamp relay. GO to
No
INSTALL a new fog lamp relay. TEST the system
for normal operation.
Yes
INSTALL a new fog lamp switch. TEST the
system for normal operation.
No
REPAIR Circuit 188 (WH/BK) for short. TEST the
system for normal operation.
No
REPAIR Circuit 1205
(BK). TEST the system
for normal operation.
Q3 .