• Richa Shetty

What are DTC (Diagnostic Trouble Codes)? Everything you Need to Know

DTC (Diagnostic Trouble Codes) codes help you understand what needs to be fixed so you can keep your vehicle safe and healthy. A DTC code Diagnostic Trouble Codes or OBD-II (in light-duty vehicles) or J1939 (in heavy-duty vehicles) is a series of diagnostic trouble codes used by a vehicle’s onboard diagnostics (OBD) system to alert you when a vehicle experiences a malfunction. When the vehicle’s OBD system detects a problem, it generates a specific DTC code and transmits the alert to the vehicle’s instrument panel as a warning light. In vehicles equipped with a telematics system, the alert can be delivered directly to the fleet. Understanding DTC codes and how they integrate with your fleet software solution can help improve driver safety and deliver healthy ROI.

Know more about OBD-II - On-Board Diagnostic System | Real-Time Alerts

OBD DTC Diagnostic Trouble Codes

Categories of the OBD2 Trouble Codes

  1. Body (B-codes)

  2. Chassis (C-codes)

  3. Powertrain (P-codes)

  4. Network & Vehicle Integration (U-codes)

1. Body (B-codes)

Covers functions that are, generally, inside of the passenger compartment. These functions provide the driver with assistance, comfort, convenience, and safety.


2. Chassis (C-codes)

Covers functions that are, generally, outside of the passenger compartment. These functions typically include mechanical systems such as brakes, steering, and suspension.


3. Powertrain (P-codes)

Covers functions that include engine, transmission, and associated drivetrain accessories.


4. Network & Vehicle Integration (U-codes)

Covers functions that are shared among computers and systems on the vehicle.


Know more about the top 5 Basic Fleet Management Problems and Challenges


The second character (Number Codes)

The first letter is followed by a number, usually 0 or 1.

  • 0 – Standardized (SAE) code, also known as generic code (sometimes called global)

  • 1 – Manufacturer-specific code (sometimes called enhanced)


The third character (number)

For powertrain codes, this number tells you which vehicle subsystem has a fault. There are eight:

0 – Fuel and air metering and auxiliary emission controls

1 – Fuel and air metering

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 – Transmission

You may see an A, B, or C, which can refer to hybrid propulsion systems.

For other families of codes, refer to the definitions provided by your manufacturer. Learn more about how software can help assist driver behavior.


The fourth and fifth characters (number)

The final piece of a DTC is a number that defines the exact problem that you’re experiencing. It can be a number between zero and 99.


Contact us for a quick demo or 14-day trial to know more about Fleet Management Software and how we can help in connecting your assets in real-time to the internet. Visit our FAQ page for some frequently asked questions on fleet management.

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