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DDEC III provides indications of engine and vehicle malfunctions. The ECM monitors input received from electronic sensors. See Figure 24984 . ‪


Any faults that occur are stored as codes in the ECM's memory. These codes can be accessed in three ways: ‪

  1. A DDR can be used to read the codes. See Figure 21424 .
  2. A personal computer (PC) connected to the ECM through a translator device which converts J 1708 to RS232 protocol.
  3. The Check Engine Light (CEL) or Stop Engine Light (SEL) is illuminated.

If the CEL (a panel mounted yellow indicator light) is illuminated, diagnose the condition as soon as convenient. ‪

If the SEL (a panel mounted red indicator light) and the CEL are illuminated, a major fault occurred and immediate attention is required to avoid engine damage. Automatic engine shutdown or rampdown is available as an option. A shutdown override switch is required to allow the vehicle to be moved to a safe location during automatic shutdown or rampdown. ‪

DDEC III features programmable with a Diagnostic Data Reader (DDR) are: ‪

  • Password
  • Droop
  • Active hp braking
  • Cruise Control
  • Vehicle speed limiting
  • Vehicle speed sensor
  • Variable speed governor cruise switch
  • Idle timer shutdown
  • Idle timer between air temperatures
  • Vehicle identification number (VIN)
  • Idle adjustment
  • Progressive shifting
  • Engine protection
  • Optimized Idle

The hand-held DDR is used on engines equipped with DDEC III to display engine description, diagnostic data, fault codes, and to program the ECM calibration. A printout of the information displayed on the DDR, can be obtained by attaching a printer. The diagnostic data reader kit, J 38500-EF , includes a reader, cable, carrying case, DDEC cartridge, manual, and a 6-pin adaptor. See Figure 21424 . ‪

DDR and Printer

The SAE Standard Communications of the DDEC III system are listed in Table . Fan control inputs and outputs for DDEC III are listed in Table . The engine brake control features of DDEC III are listed in Table . DDEC III can identify faulty components and other engine-related problems by providing the technician with a diagnostic code. ‪

Listed in Table are the SAE standard communications. ‪

SAE Standard Communication

SAE J1587 protocol on J1708 hardware ‪

Diagnostics ‪

Electronic dashes ‪

Data Hub ‪

SAE J1922 protocol on J1708 hardware ‪

Traction control systems ‪

Transmission controls ‪

SAE J1939 high speed data link ‪

ECM communications on multi-block engines ‪

Vehicle controls ‪

Table SAE Standard Communications for DDEC III

Listed in Table are the fan controls for DDEC III. ‪



Coolant Temperature ‪

Single on/off fan clutch ‪

Oil Temperature ‪

Dual on/off fan clutch ‪

Air Temperature ‪

2-speed single fan ‪

Air Conditioning ‪

Modulated fan clutch ‪

Table Fan Control for DDEC III

Listed in Table are the engine brake controls with DDEC III. ‪

Engine Brake Control

Compatible with cruise control ‪

Engine brake will go and off without disabling cruise control ‪

Engine fan braking ‪

Requires fan and engine brake control ‪

Fan turn on when engine brake is on high ‪

In cruise control, engine brake operates electronically ‪

MPH activating speeds are set with DDR ‪

Cruise control, engine brake operates manually ‪

Table Engine Brake Control with DDEC III

Listed in Table are the standard sensors. ‪

Standard DDEC III Sensors

Oil Temperature ‪

Oil Pressure ‪

Coolant Level ‪

Turbo Boost ‪

Throttle Position ‪

Timing Reference ‪

Synchronous Reference ‪

Fuel Temperature ‪

Air Temperature ‪

Table Standard Sensors

Replacement of DDEC III ECM

The DDEC III ECM is a sealed, nonserviceable unit. Tag defective ECM for recore. ‪

Removal of ECM

Perform the following steps for ECM removal: ‪

  1. Carefully disengage the lock tab on the power harness and unit pump harness connectors.
  2. Remove the 30-Pin connector, 5-Pin connector, DataLink connector, vehicle interface harness and engine injector harness connections at the ECM.
  3. Remove the thru-bolts holding the ECM to the engine.
Inspection of ECM

Inspect the ECM isolators for damage and replace if required. ‪

Installation of ECM

Perform the following steps for ECM installation: ‪

  1. Mount the ECM to the engine.
  2. Secure the ECM to the engine with thru-bolts. Torque the ECM-to-engine bolts to 30-38 N m (22-28 lb ft). Torque the ECM connector hold-down screws to 2.4-2.9 N m (21-26 lb in.).
  3. Connect the two-wire and three-wire harness connections at the ECM.
  4. Engage the lock tab on the power harness and unit pump harness connectors.
  5. Turn the ignition to the "ON" position. Observe or read any diagnostic codes. If any code except code 25 is obtained, refer to Troubleshooting Manual , or call Detroit Diesel Technical Service (313) 592-7282.