CDL Air Brake System Test — The Secret to Not Failing 🛑 This is the step that kills more CDL tests than anything else. 💀 Here’s how to check your low air warning and parking brakes the right way: 1️⃣ Pump the brakes until the low air warning light and buzzer come on — that should happen before 55 PSI. 2️⃣ Keep pumping between 20–45 PSI until both parking brakes pop out — first the red, then the yellow. 3️⃣ Whatever you do… DON’T touch those brakes again. The second you do, ❌ automatic fail. It