“DTC Definition Not Found” in Cars: Decoding The Message

Automobiles have come a long way since their invention. Modern cars are now brimming with technology, turning them into more than just machines for travel. They are sophisticated entities equipped with advanced diagnostic systems to detect and report issues. At the heart of these diagnostics lie the DTCs or Diagnostic Trouble Codes. But what does it mean when your diagnostic tool displays “DTC definition not found”? Let’s delve deeper.

dtc codes

What Does DTC Mean?

Whenever your car encounters an issue, its onboard computer system (often called the Engine Control Unit or ECU) logs it. These logs are coded into Diagnostic Trouble Codes (DTCs). Think of DTCs as the car’s way of communicating its health status.

Whether it’s an engine misfire due to faulty spark plugs, an oxygen sensor malfunction, or a problem with the transmission, each issue has its own specific DTC. Connecting a diagnostic tool to the car reads the automotive diagnostic trouble code, thus helping identify the problem area.

The Mystery of “DTC Definition Not Found”

So, you’ve plugged in your diagnostic tool, expecting a straightforward diagnosis, but instead, you’re greeted with the cryptic message: “No DTC Definition Found “. What does this mean?

While the diagnostic tool has successfully read a DTC from the car’s computer, it doesn’t recognize this particular code. Besides, 0 DTC code means no codes are stored in the computer. The issue could be due to several reasons:

Outdated Diagnostic Tool:

Just like software needs updates, diagnostic tools must also be updated with the latest database of DTC definitions. An older version might not recognize newer codes introduced by car manufacturers.

Manufacturer-Specific Codes:

Some car manufacturers have their proprietary codes that might not be universally recognized by all diagnostic tools unless they are brand-specific.

Rare or Uncommon Codes:

While there’s a universal set of DTCs, many codes are less common. If the tool hasn’t been programmed with this particular code’s definition, it’ll display the “no powertrain dtc” message.

Software Glitch:

Diagnostic scanners can also experience software glitches or errors like any other tech tool. A malfunctioning tool might fail to recognize a code it should otherwise know.

What to Do if No DTC Found?

If you encounter a “No DTC Code” message, here are steps you can take:

  1. Update Your Tool: Check if your diagnostic tool has any available updates and install them. This might add the missing definitions to its database.
  2. Cross-Reference with Online Databases: There are many online platforms and forums where car enthusiasts and experts share and discuss DTCs. You might find the definition of your elusive code there.
  3. Consult the Car’s Manual: Some manufacturers list common DTCs in the car’s manual.
  4. Visit a Professional: If you cannot identify the DTC, consult with a professional mechanic or a dealership familiar with your car’s brand.

How to Read DTC Codes in Car Diagnosis?

Reading DTC (Diagnostic Trouble Codes) codes in car diagnosis, followed by their interpretation, is a structured process that involves utilizing a specific tool known as an OBD-II scanner and applying knowledge about the code meanings and corresponding vehicle systems. Here’s a detailed guide on how to go about this process:

Step 1: Gather Necessary Tools

  • OBD-II Scanner: Ensure you have a compatible OBD-II scanner. These scanners come in various forms, including handheld units, smartphone apps paired with a wireless OBD-II adapter, or professional-grade scanners.
  • Vehicle’s Manual: Having the vehicle’s manual can be handy, as it may contain specific information about the DTC codes and the location of the OBD-II port.

Step 2: Locate the OBD-II Port

  • Locate the OBD-II port in your vehicle; it’s generally found under the dashboard on the driver’s side. If you need more clarification, consult your vehicle’s manual for the exact location.

Step 3: Connect the OBD-II Scanner

  • Insert the OBD-II scanner’s connector into the port on your vehicle.
  • Turn the ignition to the “ON” position without starting the engine (or start the engine if instructed by the scanner manual).

Step 4: Scan for Codes

  • Turn on the scanner and navigate to the “Read Codes” or similar option.
  • The scanner will communicate with the vehicle’s onboard computer and retrieve any stored codes.

Step 5: Interpret the Codes

  • Once the scanner displays the codes, note them down. DTC codes typically consist of a letter followed by a series of numbers, such as “P0301”.
  • Interpreting the First Letter: The first letter in the code can give you a general idea of the system where the issue is occurring:
    • P: Powertrain, which includes the engine, transmission, and associated systems.
    • B: Body, which encompasses functionalities like airbags, power windows, etc.
    • C: Chassis, which involves parts like the anti-lock brake system.
    • U: Network & Vehicle Integration, pertains to communication between the vehicle’s systems.
  • Understanding the Numbers: The following numbers help in pinpointing the exact issue. The first digit after the letter shows if the code is universal (0) or manufacturer-specific (1). The subsequent digit reveals the subsystem related to the error, like fuel or air intake. The last two digits give the specific fault or issue. For example, a code “P0300” indicates a bad catalytic converter and a misfire detected in the cylinder. Reading these codes requires an OBD-II scanner, connecting to the vehicle’s onboard computer. You would then focus on potential issues affecting that cylinder, such as spark plugs, fuel injectors, or coil packs.

Step 6: Research the Codes

  • Look up the meanings of the codes in the manual provided with the scanner or through reliable online databases.

Step 7: Detailed Analysis

  • After identifying the problems indicated by the codes, perform a detailed analysis. This might involve:
    • Visual Inspection: Inspecting relevant parts for obvious signs of wear or damage.
    • Functional Tests: Conducting functional tests to verify the operation of components like sensors or actuators.
    • Consulting a Specialist: Consulting a specialist or a professional technician might be necessary for complex issues or manufacturer-specific codes.

Step 8: Action and Resolution

  • Based on the interpretation and analysis, undertake necessary repairs or replacements.
  • After addressing the issues, use the scanner to clear the codes and reset the onboard computer.
  • Monitor the vehicle to see if the problem recurs. If the codes return, further diagnosis may be required.

Understanding how to read and interpret DTC codes is vital in modern vehicle maintenance. It not only helps diagnose issues accurately and assists in planning the appropriate course of action to rectify them. Thus, NO DTC Code is a major issue as this codes provide valuable information, a comprehensive diagnosis often includes additional inspection and testing to resolve the problem fully.


While the “DTC definition not found” message can be a minor hurdle in car diagnostics, understanding what it implies is the first step toward troubleshooting. With the rapid evolution of car technology, staying updated and informed is key to smooth and safe driving. Remember, these codes are the car’s way of asking for attention. And as responsible drivers, it’s up to us to ensure we understand and address these requests.


Mr. Shafiqule Islam is a graduated Mechanical Engineer and has more than 15 years experience of repairing and maintenance of different brand vehicles like Toyota, Mitsubishi, Ford, Mercedes, BMW etc. He is also giving training to Mechanics. He has started writing to share his practical knowledge to Vehicle Owners, Drivers and Mechanics to keep their cars at best fit.

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