Here is what is in 04 diag manual:
Symptom:
P0573-HIGH VOLTAGE DETECTED AT THE BRAKE SWITCH
When Monitored and Set Condition:
P0573-HIGH VOLTAGE DETECTED AT THE BRAKE SWITCH
When Monitored: While the ignition is on.
Set Condition:
POSSIBLE CAUSES
BRAKE SWITCH SHORTED TO VOLTAGE
Repair Instructions:
BRAKE SWITCH SHORTED TO VOLTAGE
Repair Brake switch shorted to voltage.