Ford 2003 Mustang Workshop Manual page 3291

O4 DETERMINE IF GEM IS SENDING THE CORRECT OUTPUT
SIGNAL
Trigger the GEM active command BKFLD LOW.
Did the instrument cluster BRAKE warning indicator
illuminate?
O5 CHECK CIRCUIT BETWEEN THE PARKING BRAKE
SWITCH AND THE GEM FOR A SHORT TO GROUND
Monitor PID PRK_BRK while applying and releasing the
parking brake.
Did the PID read ON with the parking brake applied and
with the parking brake released?
O6 CHECK CIRCUIT 128 (VT/YE) AND CIRCUIT 22 (LB/BK)
FOR AN OPEN
Key in OFF position.
Disconnect: Parking Brake Switch C306.
Disconnect: GEM C201d.
Measure the resistance between the GEM C201d pin 4,
circuit 128 (VT/YE), harness side and the parking brake
switch C306 pin 1, circuit 22 (LB/BK), harness side.
Is the resistance less than 5 ohms?
O7 CHECK CIRCUIT 1205 (BK) FOR OPEN
Measure the resistance between the parking brake switch
C306 pin 2, circuit 1205 (BK), harness side and ground.
Is the resistance less than 5 ohms?
O8 CHECK CIRCUIT 128 (VT/YE) FOR A SHORT TO GROUND
Key in OFF position.
Disconnect: Parking Brake Switch C306.
Disconnect: GEM C201d.
Measure the resistance between the GEM C201d pin 4,
circuit 128 (VT/YE), harness side and ground.
No
GO to O11 .
Yes
GO to O14 .
No
GO to O9 .
Yes
GO to O8 .
No
GO to O6 .
Yes
GO to O7 .
No
REPAIR the circuit. TEST
the system for normal
operation.
Yes
INSTALL a new parking
brake switch. TEST the
system for normal
operation.
No
REPAIR the circuit. TEST
the system for normal
operation.
Yes
REPAIR or INSTALL a new
parking brake switch as
needed. TEST the system
for normal operation.