The Detroit Diesel Electronic Control System (DDEC) controls fuel injection timing and output by the electronic unit injectors (EUI) on the Series 50 Diesel engine. DDEC controls throttle and the ignition system on the Series 50G engine. The system also monitors several engine functions using electrical sensors which send electrical signals to the Electronic Control Module (ECM). The ECM then computes the incoming data and determines the correct fuel output and timing for optimum power, fuel economy and emissions. The ECM also has the ability to display warnings or shut down the engine completely (depending on option selection) in the case of damaging engine conditions, such as low oil pressure, low coolant, or high oil temperature.
The current engines have the third generation DDEC system, DDEC III. See Figure 20395 . Former Series 50 engines had DDEC II systems.
The replacement of DDEC components is based on indicated diagnostic codes leading to faulty components. Check the DDEC II Troubleshooting Guide, 6SE489, or DDEC III/IV Single ECM Troubleshooting Guide , 6SE497, for more complete information on diagnosis of components and system problems.