Everything you need to know about DTC codes

Everything you need to know about DTC codes

When a vehicle’s on-board diagnostics system detects a malfunction, it generates the appropriate diagnostic trouble code and should alert the driver via a warning light or other indicator on the vehicle’s instrument panel. (Note: There isn’t always an indicator light.) These trouble codes are often referred to as DTC codes. DTC codes help you understand what needs to be fixed so you can keep your vehicle safe and healthy.

If you have a fleet software system in place, the DTC codes will be sent in real-time to a fleet manager or technician. Having the right vehicle diagnostics software system in place to deliver fault codes in real-time may help keep your fleet running more efficiently and smoothly.

Understanding DTC codes and how they integrate with your fleet software solution can help improve driver safety and deliver healthy ROI.

DTC Meaning: What is a DTC code?

Let’s start by explaining the DTC meaning first.

DTC stands for Diagnostic Trouble Codes.

A DTC code 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. Different DTC codes represent specific problems in your vehicle.

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. The system can be set up to deliver the alert right to the maintenance department.

These codes were created by the Society of Automotive Engineers (SAE) to help vehicles comply with emission regulations. SAE is now called SAE International, and it is the professional organization that develops standards for automotive engineers.

Standard fault code list

If a vehicle’s manufacture date is 1996 or newer, it will most likely be OBD-II compliant. The vehicle’s electronic system performs self-diagnosis and reporting. Any time the system detects a problem, it records that problem as a code. That code is known as a (DTC) diagnostic trouble code.

How do DTC codes work?

Diagnostic Trouble Codes or OBD-II (in light-duty vehicles) or J1939 (in heavy-duty vehicles) trouble codes are codes that the vehicle’s OBD system uses to notify you about a problem. Each code corresponds to a fault detected in the vehicle. When the vehicle’s computer detects an issue that requires attention, it will activate the corresponding trouble code.

What does a DTC mean in a vehicle?

The engine control module (ECM) functions as the main computer on all newer model vehicles. The ECM is also commonly referred to as the engine control unit (ECU) or powertrain control module (PCM). When your vehicle’s ECM is directly connected to your company via telematics, app, or gateway, you can find out in real-time from your desk in the home office what’s going on with the vehicle. KeepTruckin’s vehicle diagnostics automatically monitors fault codes through its direct connection to on-board vehicle diagnostics.

Diagnostic trouble codes you need to look for

KeepTruckin’s onboard diagnostics monitoring system may help you avoid costly repairs and reduce vehicle downtime. With real-time notification and a description of the fault code, the fleet manager can make the appropriate decision. That may be to drive to an outside shop or have the driver return to the carrier’s home base for repairs.

Having one person monitor incoming telematics from the entire fleet brings significant advantages. For instance, the data can be used to route drivers and assign loads to trucks that do not need service.

Over time, a company can learn how to prioritize data and look for trends. This allows the company to use preventive maintenance and extend the life of its fleet by optimizing the availability of the assets.

Critical codes:

DTC codes such as high engine temperatures and low coolant levels could mean that engine failure is imminent. With real-time vehicle diagnostics, fleet managers and technicians can act quickly. They can assess the severity, recommend appropriate action immediately, and locate the nearest service center to resolve the issue before it becomes a costly and critical situation.

Interpreting DTC codes

A DTC code is five characters long. You’ll get more familiar with these over time, but there are thousands of different codes so as a driver or fleet owner, you want to know how to find the definition for any code you see in your vehicle. If you have a good comprehensive fleet management solution, the meaning of each code will be provided to you each time you are alerted with a code.

Codes are standard, and you’ll know what area of your vehicle the code refers to if you understand the structure of the code and the standard abbreviations.

The first character (letter)

OBD-II codes start with a letter that denotes the part of the vehicle that has a fault.

  • P – Powertrain. Includes engine, transmission, and associated accessories.
  • C – Chassis. Covers mechanical systems and functions: steering, suspension, and braking.
  • B – Body. Parts mainly found in the passenger compartment area.
  • U – Network & vehicle integration. Functions managed by the onboard computer system.

The second character (number)

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 also 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.

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.

Here’s an example of a complete code:

P0782 means powertrain, generic, transmission, 2-3 shift malfunction.

The best source for DTC meanings is the dealer that sold or leased the truck to you or the manufacturer who made it. Some DTCs are specific to the vehicle. Download the complete list to your device so that you can access it any time, including in areas where cellular service may be spotty. Or consider implementing a vehicle diagnostics software solution that provides definitions for you.

DTC codes and fleet management

Information gathered by a vehicle’s telematics system can include vehicle speed, fault codes, fuel usage, engine RPM, and other details. This data can be uploaded to a software interface to allow the fleet owner to efficiently monitor performance, vehicle health, and trip start and finish details.

Without a reliable fleet telematics system in place, you may need to rely on your drivers to let you know what codes are displayed. This may not be the most efficient way to handle issues that come up. If a driver doesn’t let you know there is a DTC code that needs to be addressed, you may not become aware of a serious maintenance issue right away, and the problem could worsen before it’s fixed.

You may also need to rely on drivers to give complete and accurate information to mechanics or other repair personnel. Unfortunately, at least half of all vehicles that leave a mechanic’s shop as “fixed” still have at least one unresolved issue.

A fault code, on the other hand, can give information about underlying issues that the driver may not be aware of.

Automating the DTC process

When you employ a good telematics system, DTC codes can go straight to the fleet desk. The dispatcher can tell the driver how to handle the issue and at the same time send another vehicle to take over the load if needed.

A truck equipped with an OBD-II port can quickly and easily connect to a fleet tracking system. The KeepTruckin vehicle diagnostic system is an example of a top-rated plug-and-play ELD and fleet management device.

On-board diagnostics make telematics and fleet solutions possible. Without OBD, there would be no way to transmit data. With a good vehicle diagnostics system, you can catch maintenance issues early. The KeepTruckin vehicle diagnostics gateway features help you:

  • Monitor fault codes through a direct connection to on-board vehicle diagnostics
  • Diagnose vehicle problems in real-time, some before they occur
  • Monitor speed, idle time and other details
  • Track wear and tear – calculate trends to find out what parts wear out faster than others
  • Catch and address important issues that are highlighted in reports

What your drivers need to know about DTCs

Never ignore the check engine light when it comes on and stays on. A check engine light or malfunction indicator lamp (MIL) that stays lit is an indicator of a critical problem with your vehicle that calls for urgent attention.

If your company has an onboard vehicle diagnostics system installed, contact your fleet manager. They should have received a fault code notification on their computer with a detailed description and can instruct the driver of the next step to resolve the issue.

Learn more about the KeepTruckin Vehicle Diagnostics feature and how it can help you stay on top of your vehicle conditions. Give us a call at 844-325-9230 if you any questions.

Disclaimer: All content and information on this website is for informational and educational purposes only, does not constitute financial, business, or legal advice. Although KeepTruckin strives to provide accurate general information, the information presented here is not a substitute for any kind of professional advice, and you should not rely solely on this information. Always consult a professional in the area for your particular needs and circumstances prior to making any professional, legal, business and financial or tax-related decisions.

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Jeff Edmunds

Jeff Edmunds is a transportation industry veteran. He has launched several successful businesses specializing in freight brokerage, drayage and trucking. He recently moved to a small farm in rural Utah with his wife, Carol, to start Freight Agent Coach, an online mentoring program for the independent freight broker agent, and to try his hand at market gardening.

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