TP-6200 10/12152 Section 3 Scheduled Maintenance
3.12 Detroit Diesel Engine ControlSystems
Some generator sets equipped with Detroit Diesel
enginesuse a DDEC/MDEC/ADEC system. Access the
DDEC control box inside the generator set junction box
to retrieve codes when performing routine maintenance
or troubleshooting the engine.
Note: DDC/MTU engines with MDEC/ADEC use the
550 controller to display all engine fault code
numbers. The engine operation manual provides
the fault code description.
Use the following data for informational purposes only.
Consult the engine literature for complete information
regarding DDEC/MDEC/ADEC operation and
troubleshooting. See List of Related Materials in the
Introduction section. Contact an authorized service
distributor/dealer for service or diagnostic equipment.

3.12.1 Features

The engine control system optimizes control of critical
engine functions and protects against serious engine
damage resulting from conditions such as the following:
DLow coolant level
DLow coolant pressure
DHigh coolant temperature
DLow oil pressure
DHigh oil temperature
The major components of the DDEC/MDEC/ADEC
systeminclude the electronic control module (ECM) and
engine sensors. The DDEC control box is located in the
generator set junction box.

3.12.2 DDEC Engine Diagnostics

The DDEC engine protection system monitors engine
sensors and electronic components and recognizes
system malfunctions. Critical faults light the check
engine (CEL) and stop engine (SEL) lamps on the
control box. ECM memory software logs malfunction
codes. Consult the engine operation manual or engine
service manual to identify the stored failure code. See
Figure 3-22 for the DDEC control box features.
A-343591-C
1. Diagnostic request switch
1
Figure 3-22 DDEC Control Box
Access the stored codes in one of three ways:
DPlace the switch in the DIAGNOSTIC REQUEST
position. The CEL or SEL flashes to identify the
failure.
DUse a hand-held diagnostic data reader (DDR).
Placethe switch in the DIAGNOSTIC DATAREADER
position. Plug the DDR into the control box. The DDR
displays the stored failure codes.
DUsea personal computer software package available
from the manufacturer with a translator to access
stored codes. Follow the instructions provided with
the software.

Code Types

Activecode. A code flashing on the SEL lamp indicates
a fault currently exists.
Inactive code. A code flashing on the CEL lamp
indicates a previous fault occurrence. The ECM
memory stores inactive codes with time/date
identification and the following information:
DFirst occurrence of each diagnostic code in engine
operating hours.
DLast occurrence of each diagnostic code in engine
operating hours.
DTotal time in seconds that the diagnostic code was
active.