MBE 4000 DDEC VI Troubleshooting – Section 23.2 SPN 84/FMI 3

Section 23.2
SPN 84/FMI 3

This diagnostic condition is typically VSS open circuit.‪

Section 23.2.1
Open Circuit Check

Check as follows:‪

1. Disconnect the Vehicle Speed Sensor (VSS).
2. Measure the resistance between pin 13 of the CPC connector #3 (21–pin) and pin 1 of the VSS.
   1. If the resistance is greater than 3 Ω, repair the open between pin 13 of the CPC connector #3 (21–pin) and pin 1 of the VSS. Refer to "23.2.1.1 Verify Repairs" .
   2. If the resistance is less than 3 Ω, go to step 3 .
3. Measure the resistance between pin 14 of the CPC connector #3 (21–pin) and pin 2 of the VSS sensor.
   1. If the resistance is greater than 3 Ω, repair the open wire between pin 14 of the CPC #3 connector (21–pin) and pin 2 of the VSS. Refer to "23.2.1.1 Verify Repairs" .
   2. If the resistance is less than 3 Ω, go to step 4 .
4. Measure the resistance between pin 13 of the CPC connector #3 (21–pin) and pin 1 of the VSS sensor.
   1. If the resistance greater than 3 Ω, replace the VSS. Refer to "23.2.1.1 Verify Repairs" .
   2. If the resistance is less than 3 Ω, repair the short in the harness between pins 13 and 14 of the CPC connector #3 (21–pin). 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.