J1939 cable in vehicle communication diagnostic function: DTC system and real-time monitoring

J1939 cable in vehicle communication diagnostic function: DTC system and real-time monitoring

The core of J1939 cable is CAN 2.0B extension frame, which supports complex communication requirements through the following features:

29 bit extended identifier, multi node addressing and message priority management.

Standardized Parameter Group (PGN)

Package relevant parameters (such as engine speed, oil temperature, torque) into fixed format parameter groups, with each PGN defining transmission frequency, data length, and priority.

Multi packet transmission protocol

Support data segmentation and transmission exceeding 8 bytes, meeting the real-time transmission requirements of complex diagnostic data.

J1939 cable achieves efficient fault management through diagnostic trouble codes (DTC) and diagnostic messages (DM):

DTC coding rules

Composed of SPN, FMI, OC, and CM, it uniquely identifies the type and location of the fault.

Real time fault monitoring (DM1)

When DTC becomes active, ECU immediately sends DM1 message, which is updated at a frequency of once per second until the fault is resolved.

The message contains the status of the fault light (such as red stop light, amber warning light), achieving synchronous warning between the dashboard in the driver's cabin and the maintenance terminal.

Historical fault reading (DM2)

Support reading inactive DTCs (such as intermittent faults), analyze the frequency and severity of faults based on OC (occurrence frequency) and CM (conversion mode), and optimize maintenance strategies.