Fleet Tech Tips: Diagnostic Trouble Codes


Diagnostic Trouble Codes (DTCs) are the diagnostic terminology created by the Society of Automotive Engineers (SAE) to ensure there is a uniform mechanism for reporting faults on a vehicle.

The SAE Provides International Guidelines for DTCs

These diagnostic trouble codes are generated whenever the vehicle has diagnosed an issue over several start/stop cycles of the engine, or if the issue is of significant severity. The original purpose of these codes was to allow a mechanic or workshop to connect a diagnostic tool to read a description of the issue, but with modern telematics hardware, IntelliShift can read these codes in real-time when our devices are connected to an OBD port. 

The codes themselves are categorized according to different systems. DTCs, for example, come in four variants:

1. Body (B codes) for functions related to the passenger compartment
2. Chassis (C codes) for functions outside of the passenger compartment
3. Powertrain (P codes) for functions relating to the engine, transmission, or drivetrain
4. Network & Vehicle Integration (U codes) for functions related to the vehicle computer systems

Beyond that, the code identifies if there is a generic or manufacturer-specific issue with a number. P0102, for example, indicates a powertrain issue with the Mass Airflow Sensor while B0079 is an issue with the driver seatbelt. 

For heavy-duty vehicles, the J1939 has a different approach by using Suspect Parameter Numbers, but the idea is the same. In either case, we are able to provide these codes the moment the vehicle verifies an issue. For the majority of cases, we can even give a description of the code via the Alert, Vehicle Service, or the Diagnostics tab to prepare a mechanic for needed work, often before the driver even notices their Check Engine light is on! 

IntelliShift provides general diagnostic trouble code descriptions exclusively. Some manufacturer specific codes may not adhere to the standard, which may result in a code with no description available as seen with Vinny’s P1590 code below. In this case, a quick search online can allow a mechanic to check off manufacturer specific codes. 

IntelliShift offers this information with our Vehicle Service module, as well as an engine diagnostics alert for real-time feedback. As our alerts system allows scheduling, we can even send these alerts to different contacts depending on the time of day the error occurs.

Learn more about how IntelliShift helps with vehicle maintenance.

Matt Aspinwall is a manager of solutions engineering at IntelliShift, bringing more than 10 years of experience working in the telematics space. He aims to impart fleet asset and operations management expertise to help enterprise leaders leverage business intelligence to garner total operations excellence. 


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