MBE 900 DDEC VI Troubleshooting – Section 134.2 SPN 4259/FMI 4

Section 134.2
SPN 4259/FMI 4

This diagnosis is typically injector unit pump control valve cylinders #4, #5 and #6 are shorted to ground.‪

Section 134.2.1
Short to Ground Check

Check as follows:‪

1. Disconnect the MCM 120–pin connector and use the J-48475 breakout box with the appropriate overlay and connect ONLY the Engine Harness side cable (DO NOT connect the MCM side).
2. Measure the resistance between pin 4 of the MCM 120–pin connector and ground.
   1. If the resistance is greater than 3 Ω, go to step 6 .
   2. If the resistance is less than 3 Ω, go to the next step.
3. Disconnect the #4 unit pump. See Figure "Unit Pumps #4, 5, and 6" .
   

   Figure 1. Unit Pumps #4, 5, and 6

4. Measure the resistance between either unit pump connector stud and ground.
   1. If the resistance is greater than 3 Ω, go to the next step.
   2. If the resistance is less than 3 Ω, replace the unit pump. Refer to "134.2.1.1 Verify Repairs" .
5. Measure the resistance between pin 4 of the MCM 120–pin connector and ground.
   1. If the resistance is greater than 3 Ω, repair the short to ground between pin 5 of the MCM 120–pin connector and the #4 unit pump. Refer to "134.2.1.1 Verify Repairs" .
   2. If the resistance is less than 3 Ω, repair the short to ground between pin 4 of the MCM 120–pin connector and the #4 unit pump. Refer to "134.2.1.1 Verify Repairs" .
6. Measure the resistance between pin 8 of the MCM 120–pin connector and ground.
   1. If the resistance is greater than 3 Ω, go to step 10 .
   2. If the resistance is less than 3 Ω, go to the next step.
7. Disconnect the #5 unit pump.
8. Measure the resistance between either unit pump connector stud and ground.
   1. If the resistance is greater than 3 Ω, go to the next step.
   2. If the resistance is less than 3 Ω, replace the unit pump. Refer to "134.2.1.1 Verify Repairs" .
9. Measure the resistance between pin 8 of the MCM 120–pin connector and ground.
   1. If the resistance is greater than 3 Ω, repair the short to ground between pin 9 of the MCM 120–pin connector and the #5 unit pump. Refer to "134.2.1.1 Verify Repairs" .
   2. If the resistance is less than 3 Ω, repair the short to ground between pin 8 of the MCM 120–pin connector and the #5 unit pump. Refer to "134.2.1.1 Verify Repairs" .
10. Measure the resistance between pin 6 of the MCM 120–pin connector and ground.
    1. 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.
    2. If the resistance is less than 3 Ω, go to the next step.
11. Disconnect the #6 unit pump.
12. Measure the resistance between either unit pump connector stud and ground.
    1. If the resistance is greater than 3 Ω, go to the next step.
    2. If the resistance is less than 3 Ω, replace the unit pump. Refer to "134.2.1.1 Verify Repairs" .
13. Measure the resistance between pin 6 of the MCM 120–pin connector and ground.
    1. If the resistance is greater than 3 Ω, repair the short to ground between pin 7 of the MCM 120–pin connector and the #6 unit pump. Refer to "134.2.1.1 Verify Repairs" .
    2. If the resistance is less than 3 Ω, repair the short to ground between pin 6 of the MCM 120–pin connector and the #6 unit pump. Refer to "134.2.1.1 Verify Repairs" .

Section 134.2.1.1
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.