Complete Guide of On-Board Diagnostic Codes

Posted by Spectrum Tracking on Jan 12, 2022

What is a DTC Code?

Diagnostic Trouble Code, also known as DTC Code, is the series of codes, which alert driver, if any malfunction problem within vehicle occur. When a vehicle experience the malfunction error, then DTC Codes detect it, as Vehicle Onboard Diagnostic (OBD) system is used in vehicle to detect the problem. There are variety of DTC codes for specific malfunction, and Society of Automotive Engineers creates these codes.

Where do DTCs come from?

This is main question that arise in the mind of drivers, as DTC comes from OBD system, which does not only detect the malfunction error but also give visible alert warning to driver. Warning could be brightness of engine light, thus, engine light change in the malfunction error. DTC also develop connection between OBD scanner and vehicle′s onboard computer system. OBD could be classified as OBD-I, OBD-II and J1939. OBD-II is largely used by the manufacturer of vehicles, as it has wide range of codes to alert the driver with respect to error in vehicle.

Is your vehicle OBD-II or J1939 compliant?

You might ask this question to yourself. The answer of this question is simple and clear. First, you should check vehicle manualor you can research online in order to confirm whether vehicle is OBD-II compliant or J1939 compliant. OBD-II compliant vehicle, whether it is car or light truck, both are built as well as sold in U.S. in the start of 1996. On the other hand, if your vehicle is J1939 compliant, then it is diesel engine manufactured vehicle and only heavy-duty trucks and buses came in this category.

How do you read an OBD-II DTC?

It is not an easy task to read an OBD-II DTC, as it contain five long characters, however, you will became familiar with these characters with the passage of time. As you must know about characters, if you are the car driver or light truck driver. Following are the five characters of OBD-II DTC.

First Character

  • P ‒ P Powertrain that include engine, transmission, and associated accessories
  • C ‒ C Chassis that include mechanical system and function like steering, suspension, and braking
  • B ‒ B Body included main part that found in passenger compartment area
  • U ‒ U Vehicle Integration that include such function, which are managed by onboard computer system.

Second Character

  • 0 ‒ 0 is the standardized code which is also known as generic code
  • 1 ‒ 1 means manufacturing specific code, which is also known as enhanced code

Third Character

Following are the third character of OBD-II DTC, and the number tells vehicle rider the subsystem of vehicle:

  • 0 ‒ 0 Fuel and air metering and auxiliary emission controls
  • 1 ‒ 1 Fuel and air metering
  • 2 ‒ 2 Fuel and air metering – injector circuit
  • 3 ‒ 3 Ignition systems or misfires
  • 4 ‒ 4 Auxiliary emission controls
  • 5 ‒ 5 Vehicle speed control, idle control systems, and auxiliary inputs
  • 6 ‒ 6 Computer and output circuit
  • 7 ‒ 7 Transmission

Fourth and Fifth Character

These characters detect the main problem in engine and it can be between 0 to 99

If you are still having a problem in understanding these characters, then this problem will be resolved through following example


A DTC Code Example

How do you interpret a DTC?

DTC could be interpret easily by vehicle driver, but this require certain time to detect code and characters of DTC. For example, if your vehicle is showing P0782, then this means P is equal to Powertrain, while 0 is equal to generic code, while 7 is equal to transmission, and last one is 82 which is equal to shift malfunction. This could not be easily to detect, so you could ask mechanic if malfunction error occur within vehicle.

What are common DTCs?

Following are the most common DTC that occur mostly in vehicles and help you in identifying the real malfunction in vehicle:

  • P0101 detects the malfunction within mass airflow sensor or circuit.
  • P0110 detects the malfunction in the intake air temperature sensor circuit.
  • P0606 detects the malfunction within power train control module
  • P0442 detects the malfunction within vehicle evaporation emission control system.
  • P0706 detects the malfunction within transmission range sensor circuit.
  • P0500 detects the malfunction within speed sensor.

Over here, it is important for you to understand that these DTC only detect the problem, they will not give you detail information regarding malfunction in vehicle.

How do you read a J1939 DTC?

Like OBD-II DTC has five characters, thus, J1939 DTC consists of four fields, which detect the data about the fault in vehicle. These four fields are:

  • SPN, known as Suspect Parameter Number and represents the SPN with error, and each one can be used in a DTC.
  • FMI, also known as Failure Mode Identifier, represents the type and nature of the error, which could be sensor short-circuit error, calibration error, value range violation error or incorrect update rate error.
  • OC also known as Occurrence Counter, which help in counting the number of the condition of error for every SPN.
  • CM, also known as SPN Conversion Method,describes the byte alignment in the DTC.

DTC Scan Tools for Fleet Managers

There are variety of ways that are used by the vehicle driver to scan DTC, and among such scanners, OBD-II scanner is the best.OBD-II scanner are widely used as the scan tool by fleet managers and are available at different places. However, if you are the fleet manager, than you have to manually check the vehicle engine. It is really difficult for you to check the vehicle engine by yourself; however, you could check light of the engine to identify whether is any malfunction within vehicle. Beside manually check, you as a fleet manager could select one of the best fleet management solution. Our company′s fleet management solution is the best and reliable and help you in detecting the solution in the easy way.

Our company′s fleet management solution could be used to detect the problem, as fleet management solution will not only identify the problem but it will also alert you through dashboard, which will be provided by us. What you have to do is that – you only have to plug in directly to the vehicle OBD-II port and send vehicle related data to the cloud. Afterwards, you will have two option i.e. either you will get alert through our company′s dashboard or you will get alert through notification. If malfunction within vehicle occur mostly, then Telematics solution could be used by you as the vehicle driver.

Understand DTC Easily With Telematics

To check engine light continuously might be difficult for you, as you do not have much time to identify the malfunction. That is why it is very important for the vehicle driver to use telematics solution to examine the issue with your vehicle. Hence, you can used our company′s telematics solution, which help in detecting the actual problem with vehicle and also take an appropriate action accordingly.

Company vehicle gateway plugs directly into the OBD-II or the J1939 port of a vehicle, and thus, information regarding malfunction occur within dashboard.Not only dashboard, alert could be triggered through two more ways i.e. through vehicle fault and DTC filtering. What you have to do is that – you have to purchase our company′s DTC filtering features, which help you in finding the problem and give you alert in an alarming situation.