Section 121.1
SPN 3662/FMI 14

This diagnosis is typically an open circuit, short to ground or short to power.‪

Section 121.1.1
Open Circuit, Short to Ground or Short to Power Check

Check as follows:‪

1. Check for multiple codes.
   1. If fault code 168/1 is active , service 168/1 first. Refer to "32.2 SPN 168/FMI 1" .
   2. If fault 3663/14 and 3664/14 are active in addition to 3662/14, go to step 2 .
   3. If only fault code 3662/14 is active, go to step 9 .
2. Turn the ignition OFF.
3. Disconnect the Rear Injector Harness 12–pin connector.
4. Inspect the Rear Injector Harness 12–pin connector for bent or spread pins, inspect the connector seal for damage (signs of water or oil intrusion).
   1. If the water or oil intrusion, bent or spread pins are found, repair as necessary. Refer to "121.1.1.1 Verify Repairs" .
   2. If connector shows no signs of damage, go to step 5 .
5. Turn the ignition ON (ignition ON, engine OFF).
6. Measure for voltage between pin 4 on the MCM side of the Rear Injector Harness 12–pin connector and ground.
   1. If voltage is present, repair the short to power between pin 4 of the Rear Injector Harness 12–pin connector and pin 5 of the 120–pin MCM connector. Refer to "121.1.1.1 Verify Repairs" .
   2. If no voltage is present, go to step 7 .
7. Measure for voltage between pin 7 on the MCM side of the Rear Injector Harness 12–pin connector and ground.
   1. If voltage is present, repair the short to power between pin 7 of the Rear Injector Harness 12–pin connector and pin 7 of the 120–pin MCM connector. Refer to "121.1.1.1 Verify Repairs" .
   2. If no voltage is present, go to step 8 .
8. Measure for voltage between pin 11 on the MCM side of the Rear Injector Harness 12–pin connector and ground.
   1. If voltage is present, repair the short to power between pin 11 of the Rear Injector Harness 12–pin connector and pin 7 of the 120–pin MCM connector. See Figure "120–pin MCM Connector" . Refer to "121.1.1.1 Verify Repairs"
   2. If no voltage is present, contact the Detroit Diesel Customer Support Center at 313–592–5800 for MCM replacement authorization.
   

   Figure 1. 120–pin MCM Connector

9. Turn the ignition OFF.
10. Disconnect the Rear Injector Harness 12–pin connector.
11. Measure the resistance between pin 4 and pin 1 on the valve cover side of the injector harness. If usingJ-48671–10 , measure between injector #4 pins 3 and 4.
    1. If the resistance is greater than 3 Ω, go to step 13 .
    2. If the resistance is less than 3 Ω, go to step 12 .
12. Measure the resistance between pin 4 on the valve cover side of the Rear Injector Harness and ground. If using J-48671–10 , measure between injector #4 pin 3 and ground.
    1. If the resistance is greater than 3 Ω, repair the open between pin 4 of the Rear Injector Harness and pin 5 of the MCM 120–pin connector. Refer to "121.1.1.1 Verify Repairs" .
    2. If the resistance is less than 3 Ω, go to step 13 .
13. Remove the upper valve cover.
14. Disconnect injector #4.
15. Measure the resistance between pin 4 on the valve cover side of the Rear Injector Harness and pin 3 of the injector #4 harness connector. If using J-48671–10 , measure between injector #4 pin 3 and the injector #4 harness connector pin 3.
    1. If the resistance is greater than 3 Ω, replace the under valve cover injector harness. Refer to "121.1.1.1 Verify Repairs" .
    2. If the resistance is less than 3 Ω, go to step 16 .
16. Measure the resistance between pin 1 on the valve cover side of the Rear Injector Harness and pin 4 of the injector #4 harness connector. If using J-48671–10 , measure between injector #4 pin 4 and the injector #4 harness connector pin 4.
    1. If the resistance is greater than 3 Ω, replace the under valve cover injector harness. Refer to "121.1.1.1 Verify Repairs" .
    2. If the resistance is less than 3 Ω, replace injector #4. Refer to "121.1.1.1 Verify Repairs"

Section 121.1.1.1
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.