2005 Commercial Driver’s License Manual If the lamp stays on after the bulb check, or goes on once you are underway, you may have lost ABS control. In the case of towed units manufactured before it was required by the Department of Transportation, it maybe difficult to tell if the unit is equipped with ABS. Look under the vehicle for the ECU and wheel speed sensor wires coming from the back of the brakes. 2.18.4 – How ABS Helps You When you brake hard on slippery surfaces in a vehicle without ABS, your wheels may lockup. When your steering wheels lockup, you lose steering control. When your other wheels lockup, you may skid, jackknife, or even spin the vehicle. ABS helps you avoid wheel lockup and maintain control. You mayor may not be able to stop faster with ABS, but you should be able to steer around an obstacle while braking, and avoid skids caused by over braking.