Ford 2003 Mustang Workshop Manual page 3515

Is the resistance greater than 10,000 ohms?
A2 CHECK THE PARKING BRAKE SWITCH
Disconnect: Parking Brake Switch C306.
Measure the resistance between DRL module C1030 Pin
6, Circuit 22 (LB/BK), harness side and ground.
Is the resistance greater than 10,000 ohms?
A3 CHECK VOLTAGE TO THE DRL MODULE
Measure the voltage between DRL module C1030 Pin 2,
Circuit 477 (LB/BK), harness side and ground.
Is the voltage greater than 10 volts?
A4 CHECK IGNITION SENSE INPUT
Key in ON position.
Measure the voltage between DRL module C1030 Pin 3,
Circuit 298 (VT/OG), harness side and ground.
Yes
INSTALL a new parking brake
signal switch and bracket.
TEST the system for normal
operation.
No
REPAIR the circuit. TEST the
system for normal operation.
Yes
GO to A4 .
No
REPAIR the circuit. TEST the
system for normal operation.
Yes
GO to A5 .
No
REPAIR the circuit. TEST the
system for normal operation.