MBE 900 DDEC VI Troubleshooting – Section 99.3 SPN 2797/FMI 5

Section 99.3
SPN 2797/FMI 5

This diagnosis is typically injector #1, #2 and #3 unit pump control circuits are shorted to battery/power.‪

Section 99.3.1
Short to Battery/Power Check

Check as follows:‪

1. Turn the ignition OFF.
2. Disconnect the MCM 120–pin connector.
3. Using the J-48475 breakout box and appropriate overlay, connect the MCM side of the harness ONLY.
4. Turn the ignition ON (key ON, engine OFF).
5. Measure the voltage between pin 15 of the J-48475 breakout box and ground.
   1. If voltage is greater than 0.5 V, contact the Detroit Diesel Customer Support Center at 313–592–5800 for authorization to replace the MCM..
   2. If no voltage is present, go to the next step.
6. Turn the ignition OFF.
7. Connect the Engine Harness side of the J-48475 breakout box.
8. Turn the ignition ON (key ON, engine OFF).
9. Disconnect the #1 unit pump.
10. Measure the voltage between pin 14 of the MCM 120–pin connector and ground.
    1. If voltage is present, repair the short circuit to power between pin 14 of the MCM 120–pin connector and the #1 unit pump. See Figure "Unit Pumps #1, 2, and 3" . Refer to "99.3.1.1 Verify Repairs" .
    2. If no voltage is present, go to the next step.
    

    Figure 1. Unit Pumps #1, 2, and 3

11. Disconnect the #2 unit pump.
12. Measure the voltage between pin 10 of the MCM 120–pin connector and ground.
    1. If voltage is present, repair the short circuit to power between pin 10 of the MCM 120–pin connector and the #2 unit pump. See Figure "Unit Pumps #1, 2, and 3" . Refer to "99.3.1.1 Verify Repairs" .
    2. If no voltage is present, go to the next step.
13. Disconnect the #3 unit pump.
14. Measure the voltage between pin 12 of the MCM 120–pin connector and ground.
    1. If voltage is present, repair the short circuit to power between pins 12 of the MCM 120–pin connector and the #3 unit pump. See Figure "Unit Pumps #1, 2, and 3" . Refer to "99.3.1.1 Verify Repairs" .
    2. If no voltage is present, repair the short circuit to power between pins 10, 12 and/or 14 of the MCM 120–pin connector and unit pumps #1, 2, or 3. Refer to "99.3.1.1 Verify Repairs" .

Section 99.3.1.1
Verify Repairs

Verify repairs as follows:‪

1. Turn ignition OFF.
2. Reconnect any electrical connections that were disconnected to perform the diagnosis.
3. Clear codes with DDDL 7.0 or latest version.
4. Start and bring engine up to operating temperature (over 140°F/60°C).
5. Verify operation is satisfactory and no warning lamps illuminate. If warning lamps illuminate, troubleshoot the codes. If assistance is required, call the Detroit Diesel Customer Support Center at 313–592–5800.