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An improved vehicle engine sensor harness which virtually eliminates the potential for wire chafing damage has replaced the former harness on all Detroit Diesel Series 60 DDEC II engines. This change took effect approximately October 30, 1992. See Figure 25924 . ‪

Typical DDEC II Engine Sensor Harness

Detroit Diesel has found instances of chafing on the sensor connector harness (part number 8929468) used on DDEC II engines. The chafing can occur at the end of the plastic tee-coupling where the wires from the 30-way connector enter the coupling. See Figure 25922 . The chafing results from the absence of abrasion-resistant, convoluted tubing around the wires. Installing convoluted tubing is impractical due to the shortness of the wires at this point. With no abrasion-resistant material surrounding the wires, the rough plastic ridges inside the leg of the tee-coupling can cut through the wire coatings, exposing the wires to moisture and potential shorting. Shorting can result in the logging of false DDEC trouble codes. ‪

Former Engine Sensor Harness Showing Abrasion Point

To eliminate this concern, engine sensor harness 8929468 has been improved. The improved harness is identical to the former harness, except that abrasion-resistant tape is now wrapped around the short length of 30-way connector wires where they enter the tee-coupling. See Figure 25923 . This reduces the potential for wire damage caused by abrasion. ‪

Improved Engine Sensor Harness with Abrasion-resistant Tape

Diagnostic Procedures

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, refer to the Detroit Diesel Single ECM Troubleshooting Manual, (6SE497). Start by reading the "Basic Knowledge Required" section before attempting to diagnosis electrical faults. ‪

The DDEC II ECM provides the following electrical connections: ‪

  • One 6-way connection at the ECM for battery power and ground.
  • Two 5-way connections at the ECM for the injectors.
  • A 30-way connection at the ECM for all engine electrical connections. (Engine Sensor Harness)
  • A 30-way connection at the ECM for all cab electrical connections. (Vehicle Interface Harness)

Repair and Replacement of DDEC II Engine Sensor Harnesses

To determine if repair is possible or replacement is necessary, perform the following procedure. See Figure 25501 . ‪

Flowchart for Repair or Replacement of Engine Sensor Harness

Removal of DDEC II Engine Sensor Harnesses

Remove the DDEC II engine sensor harness as follows: ‪

  1. Disengage the locking tang on each individual sensor connector body. See Figure 25454 .

    1. Locking Tang ‪

    2. Connecting Body ‪

    Typical Sensor Connector Locking Tang

  2. Grasp the connector body and gently pull it from the sensor.
  3. Remove the five bolts securing the metal harness clips to the engine.
  4. Remove the 30-pin connector from the ECM by loosening the connector attaching bolt. Carefully pull the connector from the ECM and remove the harness from the engine.
Inspection of DDEC II Engine Sensor Harness

Inspect the engine sensor harness for the following damage: ‪

If the 30-way connector wires do not have a protective covering at the tee, Detroit Diesel recommends wrapping abrasion-resistant tape around the 30-way connector wires where the tee-coupling end clamps onto them, using the following procedure: ‪

  1. With the harness on or off the engine, open the plastic tee-coupling by disengaging the locking tabs (two on each side). See Figure 25923 . Remove the coupling.
  2. Apply two or three wraps of abrasion-resistant tape such as Polyken 266 Black Tape*, or equivalent, around the 30-way connector wires where the tee-coupling clamps onto them. See Figure 25923 . This reduces the potential for wire damage caused by abrasion.
  3. Reinstall the tee-coupling on the harness and check to make sure the tape extends a minimum of 1/2 inch outside the arm of the tee. Add an additional wrap of tape, if necessary.
  4. Secure the tee-coupling in place by engaging the locking tabs.

    Note: * Polyken 267 Black Tape is available from the following supplier in a 1 in. (25.4 mm) wide, 100 foot (30.5 m) long roll: Eliot Tape, 1902 Rochester Industrial Highway, Rochester Hills, MI 48309 Phone: (248) 652-4010 Fax: (248) 652-6591

Installation of DDEC II Engine Sensor Harness

Install the DDEC II engine sensor harness as follows: ‪

  1. Install the 30-pin connector to the ECM, and torque the connector body attaching bolt to 0.79-1.47 Nm (7-13 lbin.) torque.
  2. If removal of the harness attaching clips from the engine is required, unscrew and remove them from the cylinder block by rotating in a counterclockwise direction.
  3. Install the bolts securing the harness clips to the engine. Torque to 30-38 Nm (22-28 lbft).

    Note: To ensure proper engine sensor harness support, all missing and damaged harness clips must be replaced.

  4. Carefully plug the two-pin and three-pin harness connectors into the appropriate sensors.