DDEC III/IV Single ECM Troubleshooting

Section 66.3 Troubleshooting Flash Code 66

Section 66.3
Troubleshooting Flash Code 66

The following procedure will troubleshoot Flash Code 66.‪

Section 66.3.1
Determine Failure

The following procedure will enable you to determine the failure.‪

  1. Code s 076/0, knock level above normal range - A Failure Mode Identifier (FMI) of 0 is used to advise the user that the knock level is too high to allow the electronics to compensate for it. Troubleshoot this as a mechanical problem.
  2. Code s 076/7, knock level torque reduction - An FMI of 7 is used to advise the user the loss of engine power is due to the engine electronics trying to adjust the fueling to further reduce the knock level. Clear the code and retest. If the code continues to occur, contact Detroit Diesel Technical Service.
  3. For code s 076/3, knock sensor input voltage high, refer to "66.3.2 Check Signal to Noise Enhancement Filter Module / Knock Sensor" .
  4. For code s 076/4, knock sensor input voltage low; refer to "66.3.3 Check for Open" .

Section 66.3.2
Check Signal to Noise Enhancement Filter Module / Knock Sensor

Perform the following steps to check the Signal to Noise Enhancement Filter (SNEF) and knock sensor.‪

  1. Unplug the SNEF module.
  2. Turn ignition ON.
  3. Plug in DDR. Read codes.
    1. If code s 076/4 is logged, refer to "66.3.4 Check Connectors" .
    2. If code s 076/3 is logged, refer to "66.3.5 Check for Short to (+)" .

Section 66.3.3
Check for Open

Perform the following steps to check for an open:‪

  1. Unplug SNEF module.
  2. Install a jumper wire between cavity B and E.
  3. Turn ignition ON.
  4. Plug in DDR. Read codes.
    1. If code s 076/3 is logged, refer to "66.3.4 Check Connectors" .
    2. If code s 076/4 is logged, refer to "66.3.7 Check for Short to Ground" .

Section 66.3.4
Check Connectors

Perform the following steps to check the connectors.‪

  1. Check connectors at ECM and SNEF module.
    1. If the connectors are in good condition, replace the SNEF module. Refer to "66.3.9 Verify Repairs" .
    2. If the connectors are damaged, repair and refer to "66.3.9 Verify Repairs" .

Section 66.3.5
Check for Short to (+)

Perform the following steps to check for a short to positive (+).‪

  1. Turn ignition OFF.
  2. Disconnect the engine sensor harness. See Figure "Series 50 Gas Engine Sensor Harness" .
    Click to see this graphic in a separate window

    Figure 1. Series 50 Gas Engine Sensor Harness

  3. Measure resistance between cavity B and E of the SNEF module connector.
    1. If the measured resistance is less than 1,000 Ω, the wires are shorted to each other. Repair the wires and refer to "66.3.9 Verify Repairs" .
    2. If the measured resistance is greater than 1,000 Ω, refer to "66.3.6 Check for Ground" .

Section 66.3.6
Check for Ground

Perform the following steps to check for a ground:‪

  1. Measure resistance between cavity D and battery ground.
    1. If the measured resistance is greater than 1,000 Ω, the ground wire is open. Repair the open and refer to "66.3.9 Verify Repairs" .
    2. If the measured resistance is less than 1,000 Ω, replace the SNEF module and refer to "66.3.9 Verify Repairs" .

Section 66.3.7
Check for Short to Ground

Perform the following steps to check for a short to ground.‪

  1. Turn ignition OFF.
  2. Remove jumper wire.
  3. Disconnect the engine harness connector.
  4. Measure resistance between cavity E of the SNEF connector and a good ground.
    1. If the measured resistance is less than 1,000 Ω, the signal wire (#976) is shorted to battery (-). Repair or replace the wire and refer to "66.3.9 Verify Repairs" .
    2. If the measured resistance is greater than 1,000 Ω, replace the knock sensor and refer to "66.3.8 Check for Signal Open" .

Section 66.3.8
Check for Signal Open

Perform the following steps to check for a signal open.‪

  1. Insert jumper wire between E and C of the SNEF module connector.
  2. Unplug the engine sensor harness connector.
  3. Measure resistance between L2 (#976) and X1 (#573).
    1. If the measured resistance is greater than 1,000 Ω, wire #976 is open. Repair or replace the wire and refer to "66.3.9 Verify Repairs" .
    2. If the measured resistance is less than 1,000 Ω, refer to "66.3.4 Check Connectors" .

Section 66.3.9
Verify Repairs

Perform the following steps to verify repairs.‪

  1. Hook up all connectors.
  2. Start and run the engine.
  3. Operate under load. Road test.
  4. Turn engine off.
  5. Turn ignition ON.
  6. Plug in DDR. Read logged codes.
    1. If no codes are logged, troubleshooting is complete.
    2. If code s 076/x is logged, all system diagnostics are complete. Please review this section from the first step to find the problem. Refer to "66.3.1 Determine Failure" , or contact Detroit Diesel Technical Service.


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

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