How does the brake light work on a GMC C6500?
How does the brake light work on a GMC C6500? The low air pressure switch turns on the PRIMARY BRAKE warning lamp when the engine is started, and the lamp remains on until the system reaches normal pressure. If the system air pressure drops below 503 kPa (73 psi), when the ignition is on, the low air pressure switch turns on the warning lamp and the module sounds a constant tone alarm. When does the GMC C6500 aux warning light and alarm sound? If the system air pressure drops below 503 kPa (73 psi), when the ignition is on, the...