In a truck fault code on a data bus, which field specifies the failure mode category?

In a truck fault code on a data bus, which field specifies the failure mode category?

• A. System ID
• B. Parameter ID
• C. Failure Mode Identifier
• D. Message ID

Answer: (C)

In truck data-bus fault codes, the field that communicates what kind of problem occurred is the Failure Mode Identifier. This field is dedicated to describing the nature of the fault—the category of failure—such as a sensor reading out of range, a wiring or circuit fault, or a mechanical fault. It stays focused on how the failure happened, independent of which system or which specific parameter triggered the code. That’s why it’s the best choice: the System ID tells you which subsystem is involved, and the Parameter ID tells you which parameter within that subsystem is affected, while the Message ID points to the particular bus frame carrying the data. The Failure Mode Identifier ties it together by specifying the type of failure, enabling consistent interpretation across components and helping you diagnose the root cause quickly. For example, you might see a fault associated with the engine’s oil pressure parameter, but the FMI will indicate whether the issue is a sensor fault, a signal circuit fault, or an actual pressure fault, guiding the repair approach.

In truck data-bus fault codes, the field that communicates what kind of problem occurred is the Failure Mode Identifier. This field is dedicated to describing the nature of the fault—the category of failure—such as a sensor reading out of range, a wiring or circuit fault, or a mechanical fault. It stays focused on how the failure happened, independent of which system or which specific parameter triggered the code.

That’s why it’s the best choice: the System ID tells you which subsystem is involved, and the Parameter ID tells you which parameter within that subsystem is affected, while the Message ID points to the particular bus frame carrying the data. The Failure Mode Identifier ties it together by specifying the type of failure, enabling consistent interpretation across components and helping you diagnose the root cause quickly. For example, you might see a fault associated with the engine’s oil pressure parameter, but the FMI will indicate whether the issue is a sensor fault, a signal circuit fault, or an actual pressure fault, guiding the repair approach.