DDEC III/IV Single ECM Troubleshooting

Section 28.3 Troubleshooting Flash Code 28

Section 28.3
Troubleshooting Flash Code 28

The following procedure will troubleshoot Flash Code 28.‪

Section 28.3.1
Multiple Code Check

Perform the following steps to check for multiple codes. ‪

  1. Turn vehicle ignition switch ON.
  2. Plug in DDR.
  3. Read active codes.
    1. If code 172/4 was logged and there are no other codes logged, refer to "28.3.2 Sensor Check" .
    2. If code 172/4 and any of the following codes 110/3, 175/3, 174/3, 72/3 or 102/3 were logged, refer to "90.1 Description of Engine Sensor Harness" .
    3. If code 172/4 and any code except the following were logged 110/3, 175/3, 174/3, 72/3 or 102/3, refer to "28.3.2 Sensor Check" .

Section 28.3.2
Sensor Check

Perform the following steps to check the sensor.‪

  1. Turn vehicle ignition OFF.
  2. Disconnect the ATS connector. See Figure "Engine Harness to Air Temperature Sensor Connector" .
    Click to see this graphic in a separate window

    Figure 1. Engine Harness to Air Temperature Sensor Connector

  3. Start engine and run until Check Engine light comes on, or for eight minutes.
  4. With engine still running, read active codes.
    1. If code 172/4 and any other codes were logged, refer to "28.3.4 Check for Short" .
    2. If 172/3 and any other codes except 172/4 were logged, refer to "28.3.3 Check Air Temperature Sensor Connectors" .

Section 28.3.3
Check Air Temperature Sensor Connectors

Perform the following steps to check the ATS connector. ‪

  1. Check terminals at the ATS connector (both sensor and harness side) for damage; bent, corroded and unseated pins or sockets.
    1. If terminals and connectors are not damaged, replace ATS. Refer to "28.3.6 Verify Repairs" .
    2. If terminals and connectors are damaged, repair/replace wires and refer to "28.3.6 Verify Repairs" .

Section 28.3.4
Check for Short

Perform the following steps to check for a short.‪

  1. Turn the ignition OFF.
  2. Disconnect the engine harness connector at the ECM.
  3. Measure resistance between sockets N2 and Y2 on the engine harness connector. See Figure "ECM Engine Harness Connector" .
  4. Measure resistance between socket N2 and a good ground.
    1. If the resistance measurement between sockets N2 and Y2 and between socket N2 and a good ground is greater than 10 Ω or open, refer to "28.3.5 Check ECM Connectors" .
    2. If the resistance measurement between sockets N2 and Y2, or N2 and battery negative, is less than or equal to 10 Ω, the signal line #132 is shorted to the return line #452 or battery ground. Repair short. Refer to "28.3.6 Verify Repairs" .
    3. Click to see this graphic in a separate window

      Figure 2. ECM Engine Harness Connector

Section 28.3.5
Check ECM Connectors

Perform the following steps to check the ECM connectors. ‪

  1. Check terminals at the ECM harness connector (both ECM and harness side) for damage; bent, corroded and unseated pins or sockets, especially N2 and Y2 of the ECM connector.
    1. If terminals or connectors are not damaged, contact Detroit Diesel Technical Services and refer to "28.3.6 Verify Repairs" .
    2. If terminals and connectors are damaged, repair them. Refer to "28.3.6 Verify Repairs"

Section 28.3.6
Verify Repairs

Perform the following steps to verify repairs.‪

  1. Turn ignition OFF.
  2. Reconnect all connectors.
  3. Turn ignition ON.
  4. Clear codes.
  5. Start and run the engine for eight minutes.
  6. Stop engine.
  7. Read inactive codes.
    1. If no codes are displayed, troubleshooting is complete.
    2. If code 172/4 is logged with any other codes, all system diagnostics are complete. Review this section from the first step to find the error.
    3. If code 172/4 is not logged, but other codes are logged, refer to "9.1 First Step for Diagnosing a Fault Within the DDEC System" .


DDEC III/IV Single ECM Troubleshooting Guide - 6SE497
Generated on 10-13-2008

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