MBE 900 DDEC VI Troubleshooting – Section 99.2 SPN 2797/FMI 4

Section 99.2
SPN 2797/FMI 4

This diagnosis is typically injector control valve cylinder #1, 2, or 3 circuit is shorted to ground.‪

Section 99.2.1
Short to Ground Check

Check as follows:‪

1. Disconnect the MCM 120–pin connector and connect the J-48475 breakout box and appropriate overlay. Connect ONLY the Engine Harness side cable. DO NOT connect the MCM side.
2. Measure the resistance between pin 26 of the MCM 120–pin connector and ground.
   1. If the resistance is greater than 3 Ω, go to step 8 .
   2. If the resistance is less than 3 Ω, go to the next step.
3. Disconnect the 12–pin injector valve cover harness connector.
4. Measure the resistance between pin 1 on the valve cover side of the injector harness connector and ground. If you are using the injector breakout box (J-48475 ), use pin 1 of injector #1.
   1. If the resistance is less than 3 Ω,If the resistance is greater than 3 Ω, repair the short to ground between pins 26 or 27 of the MCM 120–pin connector and pins 1 and 2 on the engine side of the injector harness connector. See Figure "Injectors #1, 2, and 3" . Refer to "99.2.1.1 Verify Repairs" .
      

      Figure 1. Injectors #1, 2, and 3

   2. If the resistance is greater than 3 Ω, go to the next step.
5. Remove the cylinder #1 valve cover.
6. Disconnect the injector #1 connector.
7. Measure the resistance between either stud of injector #1 and ground.
   1. If the resistance is less than 3 Ω, replace the injector. Refer to "99.2.1.1 Verify Repairs" .
   2. If the resistance is greater than 3 Ω, replace the under valve cover injector harness. Refer to "99.2.1.1 Verify Repairs" .
8. 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 14 .
   2. If the resistance is greater than 3 Ω, go to the next step.
9. Disconnect the 12–pin injector valve cover harness connector.
10. Measure the resistance between pin 3 on the valve cover side of the injector harness connector and ground. If you are using the injector breakout box (J-48475 ), use pin 1 of injector #2.
    1. If the resistance is less than 3 Ω, go to the next step.
    2. If the resistance is greater than 3 Ω, repair the short to ground between pins 22 or 23 of the MCM 120–pin connector and pins 3 and 4 of the engine side of the injector harness connector. Refer to "99.2.1.1 Verify Repairs" .
11. Remove the cylinder #2 valve cover.
12. Disconnect the injector #2 connector.
13. Measure the resistance between either injector #2 connector stud and ground.
    1. If the resistance is less than 3 Ω, replace injector #2. Refer to "99.2.1.1 Verify Repairs" .
    2. If the resistance is greater than 3 Ω, replace the under valve cover injector harness. Refer to "99.2.1.1 Verify Repairs" .
14. Measure the resistance between pin 24 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.
15. Disconnect the 12–pin injector valve cover harness connector.
16. Measure the resistance between pin 5 on the valve cover side of the injector harness connector and ground. If you are using the injector breakout box (J-48475 ), use pin 1 of injector #3.
    1. If the resistance is greater than 3 Ω, repair the short circuit to ground between pins 24 or 25 of the MCM 120–pin connector and pins 5 and 6 on the engine side of the injector harness connector. See Figure "Injectors #1, 2, and 3" .Refer to "99.2.1.1 Verify Repairs" .
    2. If the resistance is less than 3 Ω, go to the next step.
17. Remove the cylinder #3 valve cover.
18. Disconnect the #3 injector connector.
19. Measure the resistance between either injector connector stud and ground.
    1. If the resistance is less than 3 Ω, replace the injector. Refer to "99.2.1.1 Verify Repairs" .
    2. If the resistance is greater than 3 Ω, replace the under valve cover injector harness. Refer to "99.2.1.1 Verify Repairs" .

Section 99.2.1.1
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.