Sticky Banner of Desktop Sticky Banner of Mobile
Menu Close

A Complete Guide to Understanding DTC Codes – Matrack Insight

Being a fleet owner, if your trucks break down halfway through their journey because of technical problems, it can mess up your delivery schedule and cost you money for unexpected repairs. So, how can you ensure your trucks run smoothly and avoid technical problems? 

One solution is to keep track of your engine’s performance and look out for any potential issues. By doing this, you can take action before the problem gets worse and causes bigger headaches.

Luckily, a tool called Diagnostic Trouble Codes (DTC) can help you manage your fleet of trucks more efficiently. DTC gives you remote access to codes that tell you exactly what’s wrong with your vehicle and guide you on what actions to take to keep everything running smoothly.

This article will give a basic understanding of DTC and the working principle through a comprehensive guide. It would help you manage the fleet maintenance based on these fault codes and ensure efficient performance with safety and reliability.

How do DTC Codes Work?

As the name implies, DTCs are generated by diagnosing any trouble in the automobile. A vehicle’s onboard diagnostics (OBD) system provides a series of codes to inform you about any technical fault detected in the truck. The vehicle’s electronic system performs self-diagnosis, and if it identifies a malfunction, it generates a code corresponding to that particular issue. 

Each DTC corresponds to a specific problem that either needs immediate resolution or might lead to inevitable failures in the long run. It indicates a fault and tells you what and where the issue is. The system displays the DTC through visible warnings that you can read with a scanner that plugs directly into the port of a vehicle.

Several versions of OBD interfaces have been evolved and utilized over the years to generate DTC and vary according to vehicle types and models. Today, two standards are in use to read the fault codes, which are as follows:

  • OBD-2: It is suitable for light and medium-weight vehicles
  • J1939: It is best for heavy-duty trucks and heavy equipment

These standards make the decoding process more smooth and more convenient, while manufacturer-specific DTCs are confusing to interpret without expert help. 

Types of DTC Codes

The OBD system can diagnose, identify and provide information on different issues in the vehicle. You can assess the severity of the problem through DTC and recommend appropriate maintenance actions. Some of these problems are serious and need immediate resolution.  

On the other hand, some issues which do not seem critical at the moment can have serious consequences if not tackled consciously. You may be interested in categorizing the fault based on severity. The explanation is as follows: 

Critical codes

These codes indicate problems that can cause quick breakdowns and severe damage to the vehicle. DTC corresponding to high engine temperatures and low coolant levels are some of the issues that can lead to engine failure. 

These codes persuade you to make quick and informed decisions to address the problems and avoid critical failures. You may arrange the service at the nearest service center to resolve the issue before it becomes critical and costly. 

Non-critical codes

These fault codes refer to issues that do not need urgent solutions but still require timely attention and actions to ensure good vehicle health and smooth performance. For example, emission-related engine problems can lead to excessive pollution, requiring action and maintenance procedures. 

Using DTC Codes for Managing Fleet Efficiency

Improving vehicle health and fleet performance requires predictive indications of technical issues arising in the vehicle and taking appropriate actions. DTC codes provide data on vehicle performance to help you improve the automobile’s condition, performance, and overall cost-efficiency. DTC can help you achieve several benefits in managing fleet performance. The details are as follows: 

Improving Efficiency and Productivity

Suitably maintained vehicles are valuable assets in fleet operations that ensure productivity and operational efficiency. As you get regular updates about vehicle conditions and indications about potential faults, you drive your efforts to resolve those proactively by arranging necessary maintenance activities. It will ensure fewer breakdowns, servicing, and downtime, improving overall fleet efficiency. 

Regular tracking of engine data and efficiency parameters allows you to manage and schedule maintenance activities more effectively. Suppose the DTC reveals any serious issue in any of your trucks. In that case, you can immediately substitute the faulty one with other trucks, maintaining the required service and delivery commitments. 

Gaining Cost-Efficiency

The DTC pinpoints the zone of the vehicle where the problem occurred so that you can focus on necessary servicing and maintenance that ensure improved vehicle performance. A productive and efficient fleet operation will eventually lead to cost-effective operations. 

You can achieve better fuel efficiency and reduce fuel costs by keeping vehicles in running conditions. You can avoid sudden and critical repairs by taking proactive actions that save you a lot of money.

A fast, reliable, and efficient fleet performance allows you to save time and handle more customer consignments to increase revenue. Moreover, reduced operational costs will help you follow competitive pricing strategies and improve your profit margins. 

Improving Maintenance Management

The DTC provides regular updates on vehicle performance and any abnormalities detected based on engine diagnostics. The system identifies potential technical issues and informs you through DTC so that you can analyze vehicle health and proactively plan the maintenance and repairs of your vehicles to resolve the issues. A record and history of fault codes also guide you in planning the maintenance schedule for different truck parts. 

Ensuring Better Customer service

As a commercial fleet business owner, you are expected to serve your customers by reaching their destination and completing delivery within agreed timelines. The DTC alerts you on potential faults and allows you to maintain your trucks in optimum condition. You thus ensure your trucks run faster and smoother on roads, avoid downtime and delays, and reach customer points on time. 

It helps improve your reliability and commitment toward customer service. You can reduce operational costs by improving efficiency and delivering service to customers at an affordable price which helps increase your customer base. 

Reducing Insurance Premiums 

The DTC lets you identify and resolve technical issues in your trucks, and you will likely face fewer failures, damages, or repairs to your trucks. You can convince insurance companies that you are well equipped to reduce the chances of faults and erratic behavior of your automobile that might cause accidents. 

The insurance agency will reduce the premium as they find you taking action to keep your vehicle in good running condition, thereby reducing the possibility of rising claims due to damages and repairs. In other words, by implementing a monitoring and alert system on faults, you can control expenses by reducing insurance premiums. 

Training Drivers to Address Faults

The DTC is a crucial tool to keep you and your drivers aware of any technical issues that need an immediate or early response. Your drivers should pay attention to fault codes as and when it is released. 

But sometimes, they may overlook it or adjust in other ways. So, you must have access to the facilities to identify and elaborate the codes and immediately inform your drivers to take action and arrange to service. 

The advanced telematics system sends you the fault code notification on your computer with a detailed description. You can accordingly communicate with the driver about the DTC meaning and arrange to fix the issue. 

Drivers must get training to check DTC codes for engine status and fault indications. They can take action based on the severity of the problem to avoid failures and breakdowns. 

How to Read and Interpret the DTC Codes?

It is not enough to access the DTC codes only. You must decode and interpret those into meaningful information depicting the engine status and technical issues. The definition for each fault code helps you take action accordingly in the desired direction. 

A standard list or database is available on different websites to help you interpret the codes. Your vehicle manufacturer can also provide a detailed description of each code and relevant reference material for decoding as applicable to the specific model of the vehicle.

You need a tool to check and read the fault codes and get detailed information. You can use a code reader or scan tools that identify the specific technical issue and generate data as a five-character code indicating the problem. 

But, to know what the code refers to, you can have an advanced comprehensive fleet management solution that gives the meaning of each DTC received. There are standard structures of DTC that tell you about the problem and the area of your vehicle where the problem occurs. Let us first understand the structure of the code and the standard abbreviations. 

The First Character

The first character of the DTC is always an alphabet that denotes which part of the vehicle has an issue. It has the following possible values and meanings:

  • P (Powertrain): It indicates a problem related to the engine, transmission, and fuel system.
  • C (Chassis): It refers to the chassis-related problem and identifies problems in the mechanical systems outside the passenger compartment, such as steering, suspension, and brakes 
  • B (Body): This character indicates that the problem relates to the vehicle body, which means the parts found in the passenger compartment area.
  • U (Network): This letter corresponds to a problem with the vehicle’s onboard computers and integration functions that the OBD manages.

The Second Character 

A second character is a digit, either 0 or 1, and shows whether the vehicle follows a standardized OBD interface for detecting faults or uses a manufacture-specific system. 

  • 0 denotes that the vehicle follows the OBD-II international standard recommended by the society of automotive engineers (SAE)
  • 1 represents the code related to a specific vehicle make or model and is less common. The number in the code means you need to contact the vehicle manufacturer for further clarification and action.

The Third Character 

The third character helps you determine which subsystems of that particular area are malfunctioning. There are eight numbers ranging from 1 to 8 that indicate different faults. 

For example, if the code indicates powertrain faults, the third character will tell you the exact vehicle subsystem that experiences the trouble.

  • 1 – Fuel and air metering system
  • 2 – Fuel and air metering injector circuit
  • 3 – Ignition systems or misfires
  • 4 – Auxiliary emission controls
  • 5 – Vehicle speed control, idle control systems, and auxiliary inputs
  • 6 – Computer and output circuit
  • 7 and 8 – Transmission systems 

The Fourth and Fifth Characters

The fourth and fifth characters are from a two-digit number between 0 and 99. This number refers to the specific fault index that defines the exact problem related to the vehicle subsystem, as indicated by the third character. 

You can download the complete list to your device and access it any time, or consider implementing a vehicle diagnostics software solution that provides definitions for you.

For example, you can interpret DTC P0128 as follows: 

  • The first character (P) indicates the problem is at the powertrain.
  • The second digit (0) tells the problem is not model-specific and will follow standard definitions.
  • The third character (1) reveals that the issue relates to the fuel and air metering system.
  • The fourth and fifth character refers to fault index 28, which refers to abnormal engine coolant temperature. 

Fleet Management Telematics Solutions for Troubleshooting

You may not be aware of any maintenance issues in your trucks and rely on drivers to give complete and accurate information to mechanics or other repair personnel. You may face a critical problem afterward that results in breakdown and repairs if you fail to attend to it on time. 

An efficient fleet management system based on reliable telematics technology can easily detect faults and automatically transmit the information to your fleet managers, staff, and drivers, facilitating quick decisions and actions. The information gathered by the telematics system can also include vehicle speed, fuel usage, engine condition, and other performance parameters. 

The Fleet telematics system collects data from the diagnostic port and generates alerts in the form of codes whenever any potential faults or technical issues are detected. As you receive the DTC, you can interpret them to identify the problem. You can plan for necessary maintenance or repairs to ensure the vehicles remain in good running condition. 

Matrack Solutions 

Modern technology solutions by Matrack help locate and address technical issues within the optimum cost and time. Matrack offers onboard diagnostics solutions by giving specific indications about the nature of troubles to help you decide maintenance needs accurately and resolve issues with quick actions. The Matrack detection system helps you with the following features: 

  • Monitor and generate alerts through onboard vehicle diagnostics.
  • Diagnose vehicle problems in real-time and as they are likely to occur. 
  • Monitor speed, idle time, fuel efficiency, and service schedules.
  • Analyze and calculate trends to find out failure-prone parts. 
  • Highlight frequent issues that need appropriate actions.

Matrack fleet management solution includes advanced tools that make DTC identification and analysis faster and more convenient. 


Maintaining good vehicle health with fewer faults and repairs makes your fleet operations more efficient, reliable, and cost-effective. DTC codes inform you about technical issues and let you take prompt and proactive actions to improve performance.

This article overviews DTC, its format, and decoding procedures to help you identify and resolve potential faults toward achieving maximum efficiency.