The DGC-500 Solution
The DGC-500 resolves ECU constraints by using four user-programmable timers that are accessed
through BESTCOMS. Each timer setting is described in the following paragraphs.
Pulse Cycle Time. This timer setting establishes the time, in minutes, that the DGC-500 waits before
pulsing the ECU again.
Response Timeout. This timer setting defines the length of time, in seconds, that the DGC-500 attempts
communication with the ECU when the DGC-500 is in the Pulsing state or Connecting state.
Settling Time. This timer setting controls the length of time, in tenths of seconds, that the DGC-500
gathers data after connecting to the ECU during the Pulsing state. This allows all metered values to be
sent and ramped up to their steady state values. Metered values are sent out by the ECU at different
rates as designated by the J1939 protocol. ECU values initially sent are low and the ECU takes time to
average out its own data values.
Engine Shut Down. This timer setting determines the length of time, in seconds, that the DGC-500
remains disconnected from the ECU when going from Running to Shutdown before starting the first pulse.
This timer should allow enough time for the engine to slow down so that when the DGC-500 pulses, the
ECU will not restart the engine.
Alarms and Pre-Alarms
If ECU communication is not established during the Connecting state or is lost during the Pre-Start,
Cranking, Resting, Running, or Cooling states, then a non-programmable ECU Communications Fail
alarm is annunciated. If the last pulse was unsuccessful (ECU communication was not established), then
the ECU Communications Fail pre-alarm will annunciate. The pre-alarm is checked only after the Pulsing
state and is annunciated only during the Ready state.
To clear Coolant Level alarms when ECU power support is needed, the user must first correct the
condition causing the alarm and then pulse the ECU to update the data. The user may pulse the ECU
remotely through BESTCOMS or locally by pressing the front panel pushbuttons in the ordered sequence
of Auto, Off.
Fuel Solenoid Relay
Because there is no external fuel solenoid to connect to, the fuel solenoid relay has been designated to
control ECU operating power. For example, Detroit Diesel's ECU applies fuel to the engine only after
engine speed rises above 60 rpm. The following timers control the fuel solenoid relay when the engine is
not running.
• Pulse Cycle Time - fuel solenoid is open
• Response Timeout - fuel solenoid is closed
• Settling Time - fuel solenoid is closed
• Engine Shut Down - fuel solenoid is open
Display Values (ECU Support Enabled)
The ECU is able to give the DGC-500 in-depth information about the values it sends. This makes it
possible for the DGC-500 to display accurate information when metering these values from the ECU.
After successfully pulsing the unit, the last values gathered when powering-off the ECU are displayed until
the next pulse. The following is a list of display values:
• Value - the actual value is displayed if the last pulse was successful or the engine is running.
• No Communications (abbreviated as NC) - displayed if the last pulse was unsuccessful.
• Not Applicable (abbreviated as NA) - the ECU does not monitor this data value.
• ECU Data Not Sent (abbreviated as NS) - data was not sent in the time designated by the J1939
protocol.
• Sender Failure (abbreviated as SF) - the ECU has determined a sender failure for that metered value.
NOTE
When ECU support is enabled during Pre-start and Resting, the fuel solenoid is
closed.
9355400990 Rev H DGC-500 Functional Description 3-27
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