MBE 900 DDEC VI Troubleshooting – Section 98.1 SPN 2791/FMI 3

Section 98.1
SPN 2791/FMI 3

This diagnostic condition is typically a short to power fault.‪

Section 98.1.1
Short Circuit Check

Check as follows:‪

1. Disconnect the EGR valve connector.
2. Turn the ignition ON (key ON, engine OFF).
3. Measure the voltage between pin 1 of the EGR valve connector and ground. See Figure "EGR Valve" .
   

   Figure 1. EGR Valve

   1. If the voltage is greater than 11.5 volts, repair the short to power between pin 1 of the EGR valve connector and pin 61 of the 120–pin MCM connector. Refer to "98.1.2.1 Verify Repairs" .
   2. If the voltage is less than 11.5 volts, go to step 4 .
4. Turn the ignition OFF.
5. Disconnect the 120–pin MCM connector.
6. Measure the resistance between pin 1 and pin 2 of the EGR valve connector.
   1. If the resistance is less than 5 Ω, repair the short between pin 1 and pin 2 of the EGR valve connector and pin 61 and 62 of the 120–pin MCM connector. Refer to "98.1.2.1 Verify Repairs"
   2. If the resistance is less than 5 Ω, refer to "98.1.2 Resistance and Voltage Check" .

Section 98.1.2
Resistance and Voltage Check

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

1. Turn ignition ON. Reconnect all connectors.
2. Clear codes with diagnostic tool.
3. Start and run the engine for one minute. Stop engine.
4. Measure the voltage between pin 1 of the EGR valve connector and ground.
   1. If the voltage is greater than 11.5 volts, repair the short to power between pin 1 of the EGR valve connector and pin 61 of the 120–pin MCM connector. Refer to "98.1.2.1 Verify Repairs" .
   2. If the voltage is less than 11.5 volts, go to step 5 .
5. Turn the ignition OFF.
6. Disconnect the 120–pin MCM connector.
7. Measure the resistance between pin 1 and pin 2 of the EGR valve connector.
   1. If the resistance is less than 5 Ω, repair the short between pin 1 and pin 2 of the EGR valve connector and pin 61 and 62 of the 120–pin MCM connector. Refer to "98.1.2.1 Verify Repairs" .
   2. If the resistance is less than 5 Ω, call the Detroit Diesel Customer Support Center (313–592–5800) for authorization to replace the MCM.

Section 98.1.2.1
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.