DDEC II ECM
This system utilizes an engine mounted ECM with a replaceable PROM in the DDEC II ECM and an EEPROM in the DDEC II ECM. The ECM has isolator mounts for both vibration and electrical isolation. Depending upon application, some units have fuel cooling of the ECM. The engine mounted system simplifies vehicle wiring for greater reliability.
The DDEC II ECM is a microprocessor. It is the control center of the DDEC II system. See Figure "Schematic Diagram of DDEC II" .
Figure 1. Schematic Diagram of DDEC II
The DDEC II ECM is packaged in a die-cast aluminum housing with sealed connectors, see Figure "Schematic Diagram of DDEC II" . It is mounted on the left side of the engine block.
The DDEC II consists of the following:
- The DDEC II ECM
- A replaceable EEPROM
- Connections to various engine sensors, operational displays, power and fuel injectors
Repair or Replacement of the DDEC II ECM
The DDEC II ECM is a sealed, nonserviceable unit. Tag defective ECM for recore.
Before attempting any diagnosis of the system, read Section 2, "Basic Knowledge Required," and Section 3, "Testing the DDEC System," of the DDEC II Troubleshooting Guide, 6SE489. Basic mechanical checks should be made beforehand to verify that the problem is definitely related to the electrical portion of the system. If the basic mechanical checks fail to locate the problem, start the electrical diagnosis with the Troubleshooting Charts as described in the DDEC II Troubleshooting Guide, 6SE489, or DDEC III/IV Troubleshooting Guide, 6SE497.
Figure 2. DDEC II Diagnostic Data Reader
Figure 3. DDEC II Diagnostic Reader
Removal of DDEC II ECM
Perform the following steps for ECM removal:
- Carefully disengage the lock tab on the power harness and injector harness connectors.
- Remove the five wire harness connections at the ECM.
- Remove the thru-bolts holding the ECM to the engine.
- Remove the ECM and cold plate from the engine.
Installation of DDEC II ECM
Perform the following steps for ECM installation:
- Inspect the ECM isolators for damage and replace if required.
- Mount the ECM and on the engine.
- Secure the ECM to the engine with thru-bolts. Torque the ECM-to-engine bolts to 23-27 N·m (17-20 lb·ft). Torque the ECM connector hold-down screws to 2.4-3.0 N·m (21-26 lb· in.).
- Connect the five wire harness connections at the ECM.
- Engage the lock tab on the power harness and injector harness connectors.
- Turn the ignition to the "ON" position. Observe or read any diagnostic codes. If any code except code 25 is obtained, refer to the DDEC II Troubleshooting Guide
, 6SE489, or DDEC III/IV Single ECM Troubleshooting Guide,
Diesel engine exhaust and some of its constituents are known to the State of California to cause cancer, birth defects, and other reproductive harm.
- Always start and operate an engine in a well ventilated area.
- If operating an engine in an enclosed area, vent the exhaust to the outside.
- Do not modify or tamper with the exhaust system or emission control system.
- Start the engine, and check for fuel leaks.
If the diagnostic reader is not available, the following procedure can be used to read the fault codes using the "Check Engine" light on the dashboard of the vehicle. See Figure "Dashboard Warning Lights" .
Figure 4. Dashboard Warning Lights
If the vehicle is equipped with an OEM supplied diagnostic switch, hold the switch in the "ON" position. This should be done with the ignition on and the engine not running.
If there is no diagnostic switch, locate the 12-pin Diagnostic Data Link (DDL) connector (DDEC II applications only) under the dash of the vehicle. See Figure "Examples of Diagnostic Data Link (DDL) Connector" .
Figure 5. Examples of Diagnostic Data Link (DDL) Connector
If the vehicle is equipped with an OEM supplied diagnostic switch, the switch must NOT be switched on when operating the vehicle. If this is done, the diagnostic mode line will be grounded, and the throttle will be forced to the idle position, affecting vehicle operation. This condition will not occur when a diagnostic reader is used.
These methods will cause the "Check Engine" light to begin flashing a code when the ignition is turned to the "ON" position. Code 25, for example, would be two flashes followed by a pause, followed by five more flashes. This code would indicate no trouble codes logged since the last system check. This flashing code will be repeated until the diagnostic switch is turned "OFF" or the jumper wire is removed from pins A and M (on DDEC II engines only).
If a code other than 25 is read, refer to the correct chart as instructed by the DDEC II Troubleshooting Guide, 6SE498, or DDEC III/IV Single ECM Troubleshooting Guide, 6SE497 for repair instructions.
Fault codes can be cleared from the DDEC II and III systems only by using a diagnostic reader. Follow the instructions supplied with the reader to clear the fault codes.
Note: Before beginning any repair procedures, the ignition switch must be in the "OFF" position.
Following are basic replacement procedures for the DDEC components. Components should NOT be replaced unless a defective unit has been concluded by the DDEC II Troubleshooting Guide , 6SE489, or DDEC III/IV Single ECM Troubleshooting Guide, 6SE497.
|Series 50 Service Manual - 6SE50|
|Generated on 10-13-2008|