What are Diagnostic Trouble Codes?
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What are 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 to reporting faults on a vehicle. The SAE has provided a set of international guidelines for DTCs on light duty vehicles (pick-up trucks, sedans, vans etc.).

These 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, Silent Passenger can read these codes in real-time when our devices are connected to an OBD port.

How do Diagnostic Trouble Codes Work?

The codes themselves are categorized according to different systems. DTCs 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!

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.

In Silent Passenger Telematics, we offer this data in the Vehicle Service section, as well as an Engine Diagnostics alert for real-time feedback. As our alerts system allows day/time scheduling, we can even send these alerts to different contact persons if they occur within our outside of business hours!

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