Cyclic Information

The DM1 PGN transmits active error codes in the system, irrespective of the diagnostic services explicitly initiated by a diagnostic tool. The PGN can be sent by all ECUs that support the J1939 diagnostics. The error codes can be tracked back unambiguously to the network nodes with help of the respective source addresses.

Visual Diagnostic Support

The error codes are signaled or represented via indicator lamps in the cockpit. The standard defines four different lights. These are:

• Malfunction Indicator Lamp (MIL)

  This lamp is prescribed by the OBD guidelines and signals malfunctions relevant to exhaust gas.

• Red Stop Lamp (RSL)

  Signals serious errors that require the vehicle to be stopped immediately.

• Amber Warning Lamp (AWL)

  Signals less serious errors that do not require the vehicle to be stopped.

• Protection Lamp (PL)

  This lamp is used to signal errors not due to electronics, e.g., wash water fill level too low or engine cooling temperature too high.

Four states are defined for all lamps:

• Lamp Off
• Lamp On (steady)
• Lamp flashing at 1 Hz
• Lamp flashing at 2 Hz