J1939 Interface 6-9
© 2012 HMS Industrial Networks AB
Doc.Id. HMSI-168-25
J1939 Diagnostic Messages
The DM1 (active diagnostics) and DM2 (previously active diagnostics) are the 2
most commonly used J1939 diagnostic messages. The X-gateway includes sup-
port for these 2 message types.
Using BWConfig, the user is able to configure an active or previously active diag-
nostic table (or both) for a given J1939 device. The X-gateway will update the
tables based on the contents of DM1 or DM2 messages produced on J1939 by the
device, and provide read access to the tables on Ethernet.
This section will describe how the diagnostic tables are handled. See “J1939
Diagnostic Tables” on page 3-15 for configuration details.
Diagnostic Table Format
The active and previously active diagnostic tables have the same format. The for-
mat consists of a table header followed by a list of table entries.
Table Header
The table header is a 16-bit word and provides an indication of the number of
diagnostic entries that are currently in the table. It also contains the current J1939
lamp status information. The table header content is described below.
Bit
Description
0-1
J1939 Protect lamp status.
2-3
J1939 Amber Warning lamp status.
4-5
J1939 Red Stop lamp status.
6-7
J1939 Malfunction lamp status.
8-14
Entry count. The current number of entries in the
table.
15
Table overflow indication.
Table 6-1 J1939 Diagnostic Table Header Content