Series 60 DDEC VI Troubleshooting – Section 126.1 SPN 3798/FMI 4

Section 126.1
SPN 3798/FMI 4

This diagnosis is typically proportional valve bank 2 circuit failed low.‪

Section 126.1.1
Circuit Check

Check as follows:‪

1. Turn the ignition ON (key ON, engine OFF).
2. Monitor the active codes.
3. Disconnect the front valve cover injector harness.
4. Does SPN 3798/FMI 4 become inactive?
   1. If yes, go to step 5 .
   2. If no, go to step 9 .
5. Reconnect the front valve cover injector harness.
6. Remove the upper valve cover
7. Disconnect the front Jake Brake® solenoid.
8. Does SPN 3798/FMI 4 become inactive?
   1. If yes, replace the front Jake Brake solenoid. Refer to "126.1.1.1 Verify Repairs" .
   2. If no, replace the injector wiring harness. Refer to "126.1.1.1 Verify Repairs" .
9. Disconnect the EGR valve.
10. Does SPN 3798/FMI 4 become inactive?
    1. If yes, replace the EGR valve. Refer to "126.1.1.1 Verify Repairs" .
    2. If no, go to step 11 .
11. Disconnect the Electronic Dosing Valve.
12. Does SPN 3798/FMI 4 become inactive?
    1. If yes, replace the Electronic Dosing Valve. Refer to "126.1.1.1 Verify Repairs" .
    2. If no, go to step 13 .
13. Disconnect the Fuel Cutoff Valve.
14. Does SPN 3798/FMI 4 become inactive?
    1. If yes, replace the Fuel Cutoff Valve. Refer to "126.1.1.1 Verify Repairs" .
    2. If no, go to step 15 .
15. Turn the ignition OFF.
16. Disconnect the MCM 120–pin connector.
17. Measure the resistance between pin 62 of the MCM 120–pin connector and ground.
    1. If the resistance is less than 5 Ω, repair the short to ground between pin 62 of the MCM 120–pin connector and the front injector valve cover connector, EGR Valve, Fuel Cutoff Valve and or Electronic Dosing Valve. Refer to "126.1.1.1 Verify Repairs" .
    2. If the resistance is greater than 5 Ω, go to step 18 .
18. Measure the resistance between pin 64 of the MCM 120–pin connector and ground.
    1. If the resistance is less than 5 Ω, repair the short to ground between pin 64 of the MCM 120–pin connector and the front injector valve cover connector, EGR Valve, Fuel Cutoff Valve and or Electronic Dosing Valve. Refer to "126.1.1.1 Verify Repairs" .
    2. If the resistance is greater than 5 Ω, contact the Detroit Diesel Customer Support Center at 313–592–5800 for MCM replacement.

Section 126.1.1.1
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.