6 Indicators That Your Heavy-Duty Truck Needs After-Treatment Repair

June 10, 2023

Regular maintenance is crucial for heavy-duty trucks, and it's essential to go beyond just focusing on performance-related factors. Compliance with emission regulations is a key consideration for truck owners, as excessive emissions can lead to environmental concerns and potential legal repercussions. The after-treatment system in your truck plays a vital role in reducing harmful gas emissions. However, it's important to address any issues that arise when certain components of the system fail to function properly. We will assess six important indicators that signal the need for after-treatment repair. 

What Is The After-Treatment System

To comply with stringent governmental regulations regarding truck emissions, manufacturers are required to incorporate an after-treatment system into their vehicles. This particular system is generally responsible for cleaning the exhaust gases before it is released from the truck. The after-treatment system incorporates a wide array of components, including various sensors. These sensors play a crucial role in detecting specific chemicals within the gases and taking necessary measures to ensure that the emitted gases align with local emission regulations.

The main sensors that are part of an after-treatment system usually consist of:

  • Temperature sensors
  • Engine NOx sensor
  • DPF sensor table
  • Compact mixer sensor table
  • PM sensor
  • NOx sensor

In addition to the sensors, the after-treatment system consists of multiple modules and interconnected components that collaborate to achieve the recirculation of gases with minimal levels of toxic substances. These regulations have been established as part of global efforts to mitigate the impact of greenhouse gases and alleviate global warming.

Signs Of Aftertreatment System Troubles

In certain instances, certain components of the after-treatment system may experience reduced efficiency in fulfilling their designated tasks. This can result in excessive emission of harmful substances from the truck, leading to non-compliance with local regulations governing gas emissions from trucks. To avoid such issues, it is crucial to be able to recognize signs of a malfunctioning after-treatment system, which often involves evaluating the exhaust system integrated into the truck. By promptly addressing any issues, you can ensure that your fleet remains in compliance with emission regulations.

Let’s consider some important signs that may signal troubles with your exhaust and after-treatment system. 

1. Loud Noises From The Exhaust

While it is common for trucks to produce more noise compared to other vehicles like cars, it is important to be attentive to loud noises originating from the exhaust system. The exhaust system can generate loud noises for various reasons, and its functionality plays a crucial role. When the exhaust system malfunctions, it can impact the emission of gases.

In some cases, the issue causing the loud noises may not be severe initially, but if left unaddressed, it can escalate into a more significant problem. Potential causes of loud exhaust noises include damaged or loose exhaust pipes, a worn-out muffler, a clogged catalytic converter, or a broken exhaust manifold. Each of these issues can contribute to the generation of loud noises within the system.

2. Smoke Coming From The Exhaust

It is crucial to be able to identify excessive smoke coming from the exhaust of your truck. When the exhaust emits an excessive amount of smoke, it not only indicates non-compliance with regulations but also suggests potential issues with the after-treatment system. A damaged manifold in the exhaust could contribute to both excessive smoke and noise while driving.

Another significant problem that may arise is the clogging of the selective catalytic reduction (SCR) system. The SCR system plays a crucial role in reducing harmful gases in emissions. When this system becomes clogged, the effectiveness of reducing these harmful gases is compromised, resulting in their emission through the exhaust pipe. Identifying excessive smoke and addressing potential issues with the after-treatment system and SCR system is essential for maintaining compliance and reducing harmful emissions.

3. Reduced Fuel Efficiency

Issues with the after-treatment system can significantly affect the fuel efficiency of your truck. If you observe that your truck is consuming more fuel than usual during trips, it is an important indicator that should not be ignored. Several factors can contribute to this increase in fuel consumption. 

When the after-treatment system is not functioning optimally, it can lead to incomplete combustion of fuel, resulting in wasted energy and increased fuel usage. Malfunctioning sensors or components within the system can disrupt the proper control of fuel injection and combustion processes, leading to reduced efficiency.

Addressing the underlying problem with the after-treatment system can have long-term cost-saving benefits. By restoring the system's functionality and optimizing fuel efficiency, you can minimize fuel consumption, reduce operating costs, and improve the overall performance of your truck. Therefore, it is essential to diagnose and fix any issues with the after-treatment system promptly to maximize fuel efficiency and save money in the long run.

4. Rusting Exhaust Pipes

Excessive rusting in the exhaust pipes can indicate problems with the after-treatment system. Harmful and toxic substances in the emitted gases can cause rust development. Regularly inspect the exhaust pipes for signs of rust to prevent further damage. Addressing issues promptly and maintaining a clean exhaust system will ensure optimal performance and longevity for your heavy-duty truck.

5. Consistent Vibrations From The Exhaust System

While it's normal for a truck to have some vibrations, the exhaust system should remain stable during movement. If you notice vibrations coming from the exhaust system, it could be a sign that your truck needs after-treatment repairs. These vibrations may be caused by loose parts or clogs in certain sections of the exhaust system, leading to the accumulation of hot air. Addressing these issues promptly will help maintain the proper functioning of the after-treatment system.

6. Overheating Engine

When the engine in a truck overheats, it can mean many things. An overheating engine can result from various issues. The proper functioning of the exhaust system is essential for venting air from the engine. When the exhaust system fails to effectively vent the air, it can lead to the accumulation of hot air inside the engine, causing the engine's temperature to rise. Neglecting an overheating engine can potentially damage crucial engine components and impair its overall performance. It's important to address engine overheating promptly to avoid further complications and maintain optimal engine function.


The after-treatment system in your trucks is vital for complying with emissions regulations and avoiding legal issues related to toxic gas emissions. It's crucial to be aware of signs indicating the need for repairs to this system, as it ensures your fleet remains within the regulations set by local governments. Make sure you and your drivers are familiar with the indicators discussed in this article. This knowledge can help you avoid costly legal procedures and prevent more severe breakdowns in the future. Stay proactive in maintaining your after-treatment system to ensure compliance and optimal performance.




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