MBE 4000 DDEC VI Troubleshooting – Section 75.2 SPN 729/FMI 4

Section 75.2
SPN 729/FMI 4

This diagnosis is typically a short to ground.‪

Section 75.2.1
Short to Ground Check

Check as follows: ‪

1. Disconnect the Grid Heater connector.
2. Disconnect the 120–pin MCM connector.
3. Measure the resistance between pins 3 and 4 of the Grid Heater connector.
   1. If the resistance is less than 5 Ω, repair the short between pins 3 and 4 of the Grid Heater connector and pins 92 and 95 of the 120–pin MCM connector. Refer to "75.2.1.1 Verify Repairs" .
   2. If the resistance is greater than 5 Ω, go to step 4 .
4. Measure the resistance between pin 3 of the Grid Heater connector and ground.
   1. If the resistance is less than 5 Ω, repair the short between pin 3 of the Grid Heater connector and ground. Refer to "75.2.1.1 Verify Repairs" .
   2. If the resistance is greater than 5 Ω, replace the Grid Heater.

Section 75.2.1.1
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.