Cummins Exhaust Brake Problems (Here Is How To Fix)

cummins exhaust brake problems

The exhaust brake is a crucial component of your Cummins engine, providing additional safety and control during your drive. However, like any other part, the exhaust brake may encounter issues that prevent it from working efficiently.

In this comprehensive guide, we will explore the common problems that can arise with your Cummins exhaust brake and provide step-by-step solutions to help you troubleshoot and resolve these issues.

When to Use the Exhaust Brake

Before delving into the troubleshooting process, it is essential to understand when and how to use the exhaust brake effectively.

The exhaust brake assists in slowing down your vehicle without applying the wheel-mounted brake system. Here are some situations where utilizing the exhaust brake is advantageous:

  1. Downhill Descents: Engage the exhaust brake when traveling downhill to prevent your vehicle from gaining excessive speed. The exhaust brake will help you maintain a safe and controlled descent.
  2. Off-Road Adventures: When navigating rough and uneven terrains, activating the exhaust brake can provide additional assistance in maintaining traction and control.
  3. Emergency Stops: In case of brake failure or emergencies, you can rely on the exhaust brake to slow down or stop your vehicle, ensuring your safety.

It is important to note that the exhaust brake is most effective at slower speeds. If you attempt to use it at high speeds, you may not experience its full braking power.

Common Causes of Cummins Exhaust Brake Malfunction

To effectively troubleshoot and fix your Cummins exhaust brake, it is crucial to identify the potential causes of the problem. Here are some common culprits for exhaust brake malfunctions:

  1. Blown Fuses: Faulty or blown fuses can disrupt the electrical circuit responsible for the exhaust brake’s operation.
  2. Faulty Relay: A malfunctioning relay can prevent the proper functioning of the exhaust brake.
  3. Disconnected or Damaged Wires: Loose or damaged wires can disrupt the flow of electrical signals, resulting in an inoperative exhaust brake.
  4. Issues with the ECU Connector: Problems with the Electronic Control Unit (ECU) connector can interfere with the exhaust brake’s performance.
  5. Continuity System Problems: A malfunctioning continuity system can impact the proper functioning of the exhaust brake.

Read also >> Exhaust Gas Sensor Problems (Helpful Guide)

Read also >> Exhaust Leaks (Causes, Symptoms, and Solutions)

Troubleshooting Cummins Exhaust Brake Not Working

Now that we have identified the potential causes of your Cummins exhaust brake malfunction, let’s proceed with the troubleshooting process.

Please note that before attempting any repairs, it is crucial to gather the necessary tools and have a basic understanding of automotive systems. If you are unsure or uncomfortable with performing the troubleshooting steps, it is recommended to seek professional assistance.

Problem 1: Check for Blown Fuses

Blown fuses are a common culprit for exhaust brake malfunctions. Follow these steps to check and replace any blown fuses:

  1. Locate the fuse box in your vehicle. In most cases, it is located under the hood on the driver’s side of the engine.
  2. Carefully remove the fuse box cover by unscrewing the screws or using the designated latch.
  3. Inspect each fuse for any signs of damage or being blown. If a fuse appears blown, remove it using your fingers or a fuse puller.
  4. Replace the blown fuse with a new one of the same amperage rating. Ensure the fuse is securely seated in its slot.

Problem 2: Inspect the Relay

A faulty relay can also cause your Cummins exhaust brake to malfunction. Follow these steps to inspect and replace the relay if necessary:

  1. Locate the relay box in your vehicle. It is often situated near the fuse box, but refer to your vehicle’s manual for precise instructions.
  2. Use pliers to carefully remove the suspect relay from its socket.
  3. Inspect the relay’s connectors for any signs of damage, corrosion, or burnt wires. If any issues are detected, the relay should be replaced.
  4. If the relay appears to be in good condition, check the wiring connected to it. Ensure there are no loose or burnt wires.

Problem 3: Check the Wiring System

Damaged or disconnected wires can also cause your exhaust brake to malfunction. Follow these steps to inspect and repair the wiring system:

  1. Disconnect the negative terminal of your vehicle’s battery to ensure safety.
  2. Locate the fuse box and carefully remove it to access the wiring system at the back.
  3. Inspect the wires for any signs of damage, such as fraying, cuts, or burns. Replace any damaged wires or repair them if possible.
  4. Use a multimeter to test the continuity of the wires. Connect the multimeter probes to the appropriate wire ends and ensure the reading indicates electrical continuity.

Problem 4: Check the ECU Connector

The ECU connector plays a significant role in the performance of your exhaust brake. Follow these steps to inspect and repair the ECU connector:

  1. Locate the ECU compartment in your vehicle. It is typically found inside the dashboard near the engine.
  2. Use a screwdriver to carefully remove the ECU compartment cover.
  3. Inspect the connectors inside the ECU compartment. Ensure they are properly connected and free from any damage.
  4. If any connectors appear faulty or damaged, they should be replaced with new ones.

Problem 5: Inspect the Continuity System

A malfunctioning continuity system can impair the performance of your Cummins exhaust brake. Follow these steps to inspect and restore the continuity system:

  1. Refer to the ECU connectors to identify the pins related to the continuity system. The connector should have information indicating the relevant pins.
  2. Count the pins and insert the multimeter probe into the corresponding pin on the connector. Take your time and ensure a secure connection.
  3. Proceed to the relays and connect the other multimeter probe to the relevant relay. Check for continuity and ensure the power is flowing correctly.
  4. If the continuity system is not functioning correctly, consider seeking professional assistance or consulting the Cummins customer support.

By following these troubleshooting steps, you should be able to identify and resolve the common issues that can cause your Cummins exhaust brake to malfunction. However, if the problem persists or you are unsure about performing any repairs, it is advisable to consult a professional mechanic or contact the Cummins customer support for further assistance.

Frequently Asked Questions (FAQs)

Why is my Cummins exhaust brake not working? A: There can be several reasons for the exhaust brake malfunction, including blown fuses, faulty relays, disconnected or damaged wires, issues with the ECU connector, or problems with the continuity system.

How can I fix my Cummins exhaust brake if it is not working? A: Start by checking for blown fuses and replacing them if necessary. Inspect the relays and wiring system for any issues and repair or replace them as needed. Verify the ECU connector’s condition and replace any faulty connectors. Finally, check the continuity system and ensure it is functioning correctly.

What should I do if my Cummins exhaust brake stops working after deleting the emissions system? A: If your exhaust brake ceases to function after deleting the emissions system, it is crucial to ensure that the exhaust back pressure sensor is connected correctly. Additionally, consider consulting a professional or contacting the Cummins customer support for further guidance.

Why is my Cummins exhaust brake not working on my older model truck? A: Older model trucks may have different configurations and requirements for the exhaust brake to function correctly.

Ensure the vacuum system is intact and operating correctly, as any oil or vacuum leaks can hinder the exhaust brake’s performance.

CVGT Exhaust brake issues?? Try this first before replacing your turbo! >> Check out the video below:


The exhaust brake is a valuable component of your Cummins engine, providing enhanced safety and control during your drive.

By understanding the common causes of exhaust brake malfunctions and following the troubleshooting steps outlined in this guide, you can effectively identify and resolve any issues that may arise.

However, if you are unsure or uncomfortable with performing the necessary repairs, it is always recommended to seek professional assistance to ensure the proper functioning of your Cummins exhaust brake.

Steve P.

Steve is an automotive technician, technical writer, and Managing Editor. He has held a lifelong passion for cars, with a particular interest in cars like the Buick Riviera. Steve is based in Boise, Idaho.

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