MBE 900 DDEC VI Troubleshooting – Section 23.2 SPN 84/FMI 4

Section 23.2
SPN 84/FMI 4

This diagnostic condition is typically circuit failed low.‪

Section 23.2.1
Short Circuit Check

Check as follows:‪

1. Disconnect the VSS connector.
2. Disconnect the CPC #3 connector (21–pin).
3. Measure the resistance between pin 1 and pin 2 of the VSS harness connector.
   1. If the resistance measurement is less than 5 Ω, repair the short pin 13 and pin 14 of the CPC #3 connector (21–pin).Refer to "23.2.1.1 Verify Repairs" .
   2. If the resistance measurement is greater than 5 Ω, go to step 4 .
4. Measure the resistance between pin 1 of the VSS harness connector and ground.
   1. If the resistance measurement is less than 5 Ω, repair the short to ground between pin 13 of the CPC #3 connector (21–pin) and pin 1 of the VSS harness connector. Refer to "23.2.1.1 Verify Repairs" .
   2. If the resistance measurement is greater than 5 Ω, go to step 5 .
5. Measure the resistance between pin 2 of the VSS harness connector and ground.
   1. If the resistance measurement is less than 5 Ω, repair the short to ground between pin 14 of the CPC #3 connector (21–pin) and pin 2of the VSS harness connector. Refer to "23.2.1.1 Verify Repairs" .
   2. If the resistance measurement is greater than 5 Ω, replace the VSS. Refer to "23.2.1.1 Verify Repairs" .

Section 23.2.1.1
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.