MBE 4000 DDEC VI Troubleshooting – Section 100.2 SPN 2798/FMI 4

Section 100.2
SPN 2798/FMI 4

This diagnosis is typically injector #4, 5, or 6 needle control valve circuit is shorted to ground.‪

Section 100.2.1
Short to Ground Check

Check as follows:‪

1. Disconnect the MCM 120–pin connector and connect the J-48475 breakout box and appropriate overlay.
2. Measure the resistance between pin 16 of the MCM 120–pin connector and ground.
   1. If the resistance is greater than 3 Ω, go to step 7 .
   2. If the resistance is less than 3 Ω, go to the next step.
3. Remove the cylinder #4 valve cover.
4. Disconnect the #4 adaptor frame harness.
5. Measure the resistance between either injector connector stud and ground.
   1. If the resistance is less than 3 Ω, replace the injector. See Figure "Injectors #4, 5, 6" . Refer to "100.2.1.1 Verify Repairs" .
   2. If the resistance is greater than 3 Ω, go to the next step.
   

   Figure 1. Injectors #4, 5, 6

6. Measure the resistance between pin16 of the MCM 120–pin connector and ground.
   1. If the resistance is less than 3 Ω, repair the short circuit to ground between pin 16 of the MCM 120–pin connector and injector #4. See Figure "Injectors #4, 5, 6" . Refer to "100.2.1.1 Verify Repairs" .
   2. If the resistance is greater than 3 Ω, repair the short circuit to ground between pin 17 of the MCM 120–pin connector and injector #4. See Figure "Injectors #4, 5, 6" . Refer to "100.2.1.1 Verify Repairs" .
7. Measure the resistance between pin 20 of the MCM 120–pin connector and ground.
   1. If the resistance is less than 3 Ω, go to step 12 .
   2. If the resistance is greater than 3 Ω, go to the next step.
8. Remove the cylinder #5 valve cover.
9. Disconnect the #5 adaptor frame harness.
10. Measure the resistance between either injector connector stud and ground.
    1. If the resistance is less than 3 Ω, replace the injector. See Figure "Injectors #4, 5, 6" . Refer to "100.2.1.1 Verify Repairs" .
    2. If the resistance is greater than 3 Ω, go to the next step.
11. Measure the resistance between pin 20 of the MCM 120–pin connector and ground.
    1. If the resistance is less than 3 Ω, repair the short circuit to ground between pin 20 of the MCM 120–pin connector and injector #5. See Figure "Injectors #4, 5, 6" . Refer to "100.2.1.1 Verify Repairs" .
    2. If the resistance is greater than 3 Ω, repair the short circuit to ground between pin 21 of the MCM 120–pin connector and injector #5. See Figure "Injectors #4, 5, 6" . Refer to "100.2.1.1 Verify Repairs" .
12. Measure the resistance between pin 18 of the MCM 120–pin connector and ground.
    1. If the resistance is less than 3 Ω, go to the next step.
    2. If the resistance is greater than 3 Ω, contact the Detroit Diesel Customer Support Center at 313–592–5800 for authorization to replace the MCM.
13. Remove the cylinder #6 valve cover.
14. Disconnect the #6 adaptor frame harness.
15. Measure the resistance between either injector connector stud and ground.
    1. If the resistance is less than 3 Ω, replace the injector. See Figure "Injectors #4, 5, 6" . Refer to "100.2.1.1 Verify Repairs" .
    2. If the resistance is greater than 3 Ω, go to the next step.
16. Measure the resistance between pin 18 of the MCM 120–pin connector and ground.
    1. If the resistance is less than 3 Ω, repair the short circuit to ground between pin 24 of the MCM 120–pin connector and injector #6. See Figure "Injectors #4, 5, 6" . Refer to "100.2.1.1 Verify Repairs" .
    2. If the resistance is greater than 3 Ω, repair the short circuit to ground between pin 25 of the MCM 120–pin connector and injector #6. See Figure "Injectors #4, 5, 6" . Refer to "100.2.1.1 Verify Repairs" .

Section 100.2.1.1
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.