UMAX090600 Version 1
Preliminary Documentation – May be Subject to Change
16-48
will immediately be generated that includes the new DTC. The timer is provided so that intermittent
faults do not overwhelm the network as the fault comes and goes, since a DM1 message would be
sent every time the fault shows up or goes away.
Previously active DTCs (any with a non-zero OC) are available upon request for a
DM2
message. If
there is more than one previously active DTC, the multipacket DM2 will be sent to the Requester
Address using the Transport Protocol (TP).
Should a
DM3
be requested, the occurrence count of all previously active DTCs will be reset to zero.
The OC of currently active DTCs will not be changed.
The Diagnostic function block has a setpoint
“Event Cleared only by DM11.”
By default, this is
always set to False, which means that as soon as the condition that caused an error flag to be set
goes away, the DTC is automatically made Previously Active, and is no longer included in the DM1
message. However, when this setpoint is set to True, even if the flag is cleared, the DTC will not be
made inactive, so it will continue to be sent on the DM1 message. Only when a DM11 has been
requested will the DTC go inactive. This feature may be useful in a system where a critical fault
needs to be clearly identified as having happened, even if the conditions that caused it went away.
In addition to all the active DTCs, another part of the DM1 message is the first byte which reflects
the Lamp Status. Each Diagnostic function block has the setpoint
“Lamp Set by Event in DM1”
which determines which lamp will be set in this byte while the DTC is active. The J1939 standard
defines the lamps as
‘Malfunction’, ‘Red, Stop’, ‘Amber, Warning’
or
‘Protect’.
By default, the
‘Amber,
Warning’
lamp is typically the one set by any active fault.
By default, every Diagnostic function block has associated with it a proprietary SPN. However, this
setpoint
“SPN for Event used in DTC”
is fully configurable by the user should they wish it to reflect
a standard SPN define in J1939-71 instead. If the SPN is changed, the OC of the associate error log
is automatically reset to zero.
Every Diagnostic function block also has associated with it a default FMI. The only setpoint for the
user to change the FMI is
“FMI for Event used in DTC,”
even though some Diagnostic function
blocks can have both high and low errors as shown in Table 15. In those cases, the FMI in the
setpoint reflect that of the low end condition, and the FMI used by the high fault will be determined
per Table 15. If the FMI is changed, the OC of the associate error log is automatically reset to zero.
FMI for Event used in DTC – Low Fault
Corresponding FMI used in DTC – High Fault
FMI=1, Data Valid but Below Normal Operational Range
– Most Severe Level
FMI=0, Data Valid but Above Normal Operational
Range – Most Severe Level
FMI=4, Voltage Below Normal, or Shorted to Low Source
FMI=3, Voltage Above Normal, or Shorted to High
Source
FMI=5, Current Below Normal or Open
Circuit
FMI=6, Current Above Normal or Grounded
Circuit
FMI=17, Data Valid but Below Normal Operating
Range – Least Severe Level
FMI=15, Data Valid but Above Normal Operating
Range – Least Severe Level
FMI=18, Data Valid but Below Normal Operating Range –
Moderately Severe Level
FMI=16, Data Valid but Above Normal Operating Range
– Moderately Severe Level
FMI=21, Data Drifted Low
FMI=20, Data Drifted High
