DD 15 – Section 29.1 SPN 3661/FMI 14 | Detroit Diesel Engine Troubleshooting (2024)

Section 29.1
SPN 3661/FMI 14

SPN 3659/FMI 14 is typically an open circuit, short to ground or short to power (cylinder #3).‪

Check as follows:‪

1. Check for multiple codes.
   1. If fault code 168/1 is active, service 168/1 first. Refer to "29.1.1 Verify Repairs" .
   2. If fault 3659/14 and 3660/14 are active in addition to 3661/14, go to the next step.
   3. If only fault code 3661/14 is active, go to step 10 .
2. Turn the ignition OFF.
3. Disconnect the Front Injector Harness 14–pin connector.
4. Inspect the Front Injector Harness 14–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 "29.1.1 Verify Repairs" .
   2. If connector shows no signs of damage, go to the next step.
5. Measure the resistance between pins 5 and 12 on the valve cover side of the Front Injector Harness. If using J-48671–10 , measure between injector #3 pins 1 and 2.
   1. If the resistance is greater than 3 Ω, replace the under valve cover injector harness. Refer to "29.1.1 Verify Repairs" .
   2. If the resistance is less than 3 Ω, go to the next step.
6. Disconnect the MCM 120–pin connector.
7. Measure the resistance between pin 13 of the MCM 120–pin connector and pin 5 of the Front Injector Harness 14–pin connector.

   

   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 open between pin 13 of the MCM 120–pin connector and pin 5 of the Front Injector Harness 14–pin connector. Refer to "29.1.1 Verify Repairs" .
8. Disconnect the negative battery cable.
9. Measure the resistance between the positive battery post and pin 13 of the MCM 120–pin connector.
   1. If the resistance is greater than 3 Ω, contact the Detroit Diesel Customer Support Center at 313–592–5800 for MCM replacement authorization.
   2. If the resistance is less than 3 Ω, repair the short to power between battery positive and pin 13 of the MCM 120–pin connector. Refer to "29.1.1 Verify Repairs" .
10. Turn the ignition OFF.
11. Disconnect the Front Injector Harness 14–pin connector.
12. Measure the resistance between pin 5 and pin 12 on the valve cover side of the injector harness. If using J-48671–10 , measure between injector #3 pins 1 and 2.
    1. If the resistance is greater than 3 Ω, go to the next step.
    2. If the resistance is less than 3 Ω, go to step 18 .
13. Remove the upper valve cover.
14. Disconnect injector #3.
15. Measure the resistance between pin 5 on the valve cover side of the Front Injector Harness and pin 1 of the injector #3 harness connector. If using J-48671–10 , measure between injector #3 pin 1 and the injector #3 harness connector pin 1.
    1. If the resistance is greater than 3 Ω, replace the under valve cover injector harness. Refer to "29.1.1 Verify Repairs" .
    2. If the resistance is less than 3 Ω, go to the next step.
16. Measure the resistance between pin 12 on the valve cover side of the Front Injector Harness and pin 2 of the injector #3 harness connector. If using J-48671–10 , measure between injector #3 pin 2 and the injector #3 harness connector pin 2.
    1. If the resistance is greater than 3 Ω, replace the under valve cover injector harness. Refer to "29.1.1 Verify Repairs" .
    2. If the resistance is less than 3 Ω, go to the next step.
17. Measure the resistance between pin 12 on the valve cover side of the Front Injector Harness and ground. If using J-48671–10 , measure between injector #3 pin 2 and ground.
    1. If the resistance is greater than 3 Ω, replace injector #3. Refer to "29.1.1 Verify Repairs" .
    2. If the resistance is less than 3 Ω, replace the under valve cover injector harness. Refer to "29.1.1 Verify Repairs" .
18. Measure the resistance between pin 12 on the valve cover side of the Front Injector Harness and ground. If using J-48671–10 , measure between injector #3 pin 2 and ground.
    1. If the resistance is greater than 3 Ω, repair the short to ground between pin 12 of the 120–pin MCM connector and pin 12 of the Front Injector Harness 14–pin connector. Refer to "29.1.1 Verify Repairs" .
    2. If the resistance is less than 3 Ω, go to step 19 .
19. Remove the upper valve cover.
20. Disconnect the injector #3 connector.
21. Measure the resistance between pin 12 on the valve cover side of the Front Injector Harness and ground. If using J-48671–10 , measure between injector #3 pin 2 and ground.
    1. If the resistance is greater than 3 Ω, replace injector #3. Refer to "29.1.1 Verify Repairs" .
    2. If the resistance is less than 3 Ω, replace the under valve cover injector harness. Refer to "29.1.1 Verify Repairs" .

Section 29.1.1
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.

   ENGINE EXHAUST‪
   To avoid injury from inhaling engine exhaust, always operate the engine in a well-ventilated area. Engine exhaust is toxic.‪

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.