MBE 4000 DDEC VI Troubleshooting – Section 74.3 SPN 723/FMI 4

Section 74.3
SPN 723/FMI 4

A typical diagnosis is a short to ground.‪

Section 74.3.1
Short to Ground Check

Check as follows:‪

1. Disconnect the CMP Sensor.
2. Measure the resistance between pin 1 of the CMP Sensor and ground. See Figure "MCM — Camshaft Position Sensor Schematic" .
   

   Figure 1. MCM — Camshaft Position Sensor Schematic

   1. If the resistance is greater than 5 Ω, go to step 3 .
   2. If the resistance is less than 5 Ω, replace the CMP Sensor.Refer to "74.2.1.1 Verify Repairs" .
3. Measure the resistance between pin 2 of the CMP Sensor and ground.
   1. If the resistance is greater than 5 Ω, go to step 4 .
   2. If the resistance is less than 5 Ω, replace the CMP Sensor.Refer to "74.2.1.1 Verify Repairs" .
4. Disconnect 120-pin MCM connector.
5. Measure the resistance across pins 1 and 2 of the CMP harness connector.
   1. If the resistance is greater than 5 Ω, go to step 6 .
   2. If the resistance is less than 5 Ω, repair the short between pins 1 and 2 of the CMP harness connector and pins 48 and 45 of the 120–pin MCM connector. Refer to "74.2.1.1 Verify Repairs" .
6. Measure the resistance between pin 1 of the CMP harness connector and ground.
   1. If the resistance is greater than 5 Ω, go to step 7 .
   2. If the resistance is less than 5 Ω, repair the short to ground between pin 1 of the CMP harness connector and pin 48 of the 120–pin MCM connector. Refer to "74.2.1.1 Verify Repairs" .
7. Measure the resistance between pin 2 of the CMP harness connector and pin 45 of the 120–pin MCM connector.
   1. If the resistance is greater than 5 Ω, review steps 2 through 7 . If the results are the same, contact Detroit Diesel Customer Support Center (313–592–5800).
   2. If the resistance is less than 5 Ω, repair the short to ground between pin 2 of the CMP harness connector and pin 45 of the 120–pin MCM connector. Refer to "74.2.1.1 Verify Repairs" .

Section 74.3.1.1
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.