MBE 900 DDEC VI Troubleshooting – Section 78.1 SPN 975/FMI 3

Section 78.1
SPN 975/FMI 3

This fault code indicates that there is a short to power.‪

Section 78.1.1
Short to Power Check

Check as follows:‪

1. Turn the ignition OFF.
2. Disconnect the fan control solenoid connector.
3. Turn the ignition ON (key ON, engine OFF).
4. Measure the voltage between pin 1 of the fan control solenoid connector and ground.
   1. If the voltage is greater than 11.5 volts, repair the short to power between pin 1 of the fan control solenoid connector and pin 33 of the 120–pin MCM connector. Refer to "78.1.2.1 Verify Repairs" .
   2. If the voltage is less than 11.5 volts, refer to "78.1.2 Voltage Check" .

Section 78.1.2
Voltage Check

The voltage check performed indicate that you should not be getting a code. The following is a recheck before requesting a new MCM.‪

1. Turn vehicle ignition OFF. Reconnect all connectors.
2. Turn ignition ON. Clear codes with diagnostic tool.
3. Start and run the engine for one minute. Stop engine.
4. Put the ignition switch in the OFF position
5. Disconnect the fan control solenoid connector.
6. Turn the ignition switch to the ON position.
7. Measure the voltage between pin 1 of the fan control solenoid connector and ground.
   1. If the voltage is greater than 11.5 volts, repair the short to power between pin 1 of the fan control solenoid connector and pin 33 of the 120–pin MCM connector. Refer to "78.1.2.1 Verify Repairs" .
   2. Of the voltage is less than 11.5 volts, contact the Detroit Diesel Customer Support Center (313–592–5800) for authorization to replace the MCM.

Section 78.1.2.1
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.