Ford 2003 Mustang Workshop Manual page 3741

Is the rear window defrost switch indicator ON?
H11 CHECK ICM OUTPUT
Trigger the ICM active command R DEFRLY to ON.
Measure the resistance between the heated rear window
relay pin 85, circuit 727 (YE/BK), harness side and ground.
Is the resistance less than 5 ohms?
H12 CHECK CIRCUIT 727 (YE/BK) FOR AN OPEN
Key in OFF position.
Measure the resistance between ICM C220a pin 10, circuit
727 (YE/BK), harness side and the heated rear window relay
pin 85, circuit 727 (YE/BK) , harness side.
Is the resistance less than 5 ohms?
H13 CHECK POWER TO REAR WINDOW DEFROST SWITCH
Disconnect: Rear Window Defrost Switch C241.
Key in ON position.
Measure the voltage between the rear window defrost switch
C241 pin 1, circuit 883 (PK/LB), harness side and ground.
(BR/LB). TEST the system
for normal operation.
Yes
GO to H13 .
No
GO to H12 .
Yes
GO to H16 .
No
REPAIR the circuit. TEST
the system for normal
operation.
Yes
GO to H14 .
No
REPAIR the supply circuit.
TEST the system for
normal operation.