Possible Causes

(Z1) Ground Circuit Open
Intermittent Condition
(V30) S/C Brake Switch Output Circuit
(V30) S/C Brake Switch Output Circuit Open
Brake Lamp Switch
(V32) S/C Power Supply Circuit Open
S/C Vacuum Solenoid
(V36) S/C Vacuum Sol Control Circuit Open
(V36) S/C Vacuum Sol Control Circuit Shorted To Ground
S/C Vent Solenoid
(V35) S/C Vent Sol Control Circuit Open
(V35) S/C Vent Sol Control Circuit Shorted To Ground
PCM