CDL · Antilock Brake Systems

If your ABS warning light comes on while driving:

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Correct answer

Continue driving; the brakes still work but the ABS may not be functioning fully, and the system should be checked at the next opportunity

A Engage the parking brake to slow down
B Continue driving; the brakes still work but the ABS may not be functioning fully, and the system should be checked at the next opportunity
C Stop immediately and call a wrecker
D The brakes have failed completely

Why this is the answer

If the ABS warning light illuminates while driving, the ABS is malfunctioning but the conventional brakes continue to work. You can drive carefully to your destination or to a repair shop. Adjust your driving to compensate: brake earlier and more gradually to avoid the lockup conditions ABS would normally prevent, increase following distance, and avoid panic braking that could cause uncontrolled skids. The yellow ABS light is distinct from the brake warning light (which is red and indicates a more serious problem). Have the ABS repaired at the next reasonable opportunity, and note the malfunction in your inspection log. ABS does not work in reverse on most heavy vehicles regardless of fault status.

Source: FMCSA CDL Manual 6.5.2 ABS Malfunction

Practice more questions

This question is from our CDL Practice Tests practice test. Take the full practice test to test your knowledge across all Antilock Brake Systems and other topics.

Take the Combination Vehicles practice test →

About this topic: Antilock Brake Systems

ABS prevents wheel lockup during heavy braking, preserving steering and reducing stopping distance on slick surfaces. Drivers must brake firmly, not pump, on ABS-equipped vehicles. This is one of 6 Combination Vehicles questions on antilock brake systems, each with a full explanation on a single study page.

New to this exam? Our CDL exam guide explains the format, scoring, and how to prepare.

State-specific guides

Need information for your state? Our state guides cover local requirements, fees, and what to expect on exam day.

Recommended study materials

Study guide

As an Amazon Associate, CJ Affiliate, and AWIN publisher we earn from qualifying purchases. Links above are affiliate links. Full disclosure →

If your ABS warning light comes on while driving:

Why this is the answer

Practice more questions

About this topic: Antilock Brake Systems

Related questions

Which combination vehicles are required to have ABS?

Should you pump the brakes when driving an ABS-equipped combination vehicle?

In a combination vehicle, what is the purpose of the trailer air supply valve (sometimes called the tractor protection valve control)?

What is the function of the trailer hand valve (trolley valve) and why should it NOT be used for parking?

State-specific guides

Recommended study materials

CDL Study Guide (Trivium)

CDL Practice Tests & Flashcards (Accepted Inc.)

Master the CDL Truck Driver's License (Arco)